The MP Evas were clearly designed specifically with wireless power (e.g. S2 engines) in mind, because the flight mode would be completely useless if they needed a cable to be powered. However, NERV/SEELE didn't really get access to an S2 engine until the start of the show, whose timeline from Shinji arriving in Tokyo-3 to the MPE's attack seems to be around 5-6 months - possibly longer, but definitely no more than one year.

This leaves us really just one plausible explanation: that the MP Evas were designed with the expectation that they'd figure out the power issue at some point, so they made the power system easy to modify and retrofit. The MP Evas themselves were being manufactured years before the events of the show and probably just sitting in a hangar somewhere during the events of the show, until they were fitted with S2 engines sometime between Episode 17 (Eva-04 nuking the US NERV base during an S2 engine test) and EoE. Worst comes to worst, the wings would just be useless - it's not like they take up space when not in use anyways, given that they seem to

The only other possibility is that SEELE designed (not from scratch, granted) and manufactured 9 giant robots over the course of a few months, which really pushes the bounds of plausibility.

This started off as a question but over the course of typing the post I sort of ended up answering my own question. I'll post it anyways in case anyone else has thought of this.

My NGE chronology is a bit mushy, but I seem to recall that up until Episode 22(!), the preparations were still not finalized in-universe. And the 9 were only because they didn't finish in time; the original plan was to have 12 of them!

That's right.

In ep. 22, Hyuga and Misato have a conversation about that. In the words of the Netflix sub:

Misato: Construction has begun on Eva units up through Unit 13?

So the news of the construction beginning was only received by Misato in ep.22, though it is technically possible it might have started earlier.

I'm more than sure that the EVA Series began to be manufactured after episode 19 (probably during the one month time skip between the awakening of Unit 01 and Shinji's come back).
Firstly, humanity didn't know how to explore the S2 engine's power before that happened. We know that they had some really important data on the organ at Germany, but their experiments with it were not successful. I mean, just look at what happened with Nerv's second branch. However, their research on the subject was advanced enough for Gendo to not worry about the loss of the S2 engine iself.
When Unit 01 woke up and incorporated Zeruel's S2 engine, Seele was intimidated. It was at this time that the council and Gendo began to antagonize themselves almost openly. So, I believe that they pushed for the production of the EVA series in order to accelerate their agenda and respond to what had just happened.
Episode 22 is packed with memorable moments. So the conversation between Misato and Makoto gets overshadowed. However, it does contain some interesting informations about the manufacturing status of the EVA series. Makoto suggests that production on these Evangelions have just began. Also, Nerv is building them by unconventional means, according to Misto herself. That's different from Units 05 and 06 original production schedule. Those two Evangelions were being built in Germany and everyone at Nerv's first branch was aware of that (some of their parts were even used to restore Units 00 and 02). Therefore, it is safe to assume that the original plan to build Units 05 to 13 was completely changed after the events of episode 19.

Interesting, I definitely missed that line when watching it. I suppose Evas are grown organically so there's no solid real-world reference for how long that would take, and most of the armor aside from the heads is just recycled from the stock Eva design anyways, which means they probably had at least a few sets of spare armor in stock given how often the Evas get completely wrecked in combat. If we do some hand-waving and assume that most of the components like the entry system had already been manufactured beforehand and just needed to be installed into the newly grown MPE bodies, I suppose it's plausible that they were able to pull it together in the span of a few months.

The original Units 05 and 06 which get scrapped are an interesting, as they're usually forgotten, leftover from the Production proposal, before the MP Evas existed.

Page 9-

Unit 00 Prototype: Partially damaged in its first combat. The unit is being kept on freeze.
Unit 01 Test Type: Successfully activated for the first time in Episode 01, upon which it was immediately used in actual combat.
Unit 02 Experimental Type: Currently being transported from Sasebo via aircraft carrier in the care of the U.N. Army. The final adjustments have been handled.
Unit 03 Experimental Type: Currently being constructed at an unspecified site in America.
Unit 04 Test Type: Missing number. As it disappeared in an explosion incident, its construction has been discontinued.
Unit 05 Experimental Type: Currently being constructed at an unspecified site in Germany.
Unit 06 Mass Production Model: Construction is scheduled to begin in 2016, also in Germany.

(Though Unit 05 is labelled 'experimental type' Unit 02 is also labelled that, while obvs in the show Asuka states that Unit is the first proper production type)

03's fate is the same, in the episode descriptions, with Unit 05 being transferred to Nerv in the birth of Nerv episode (which was ep 20 before getting shifted to ep 21)- possibly to replace Unit 02 as the ep 19 description has Asuka 'heavily wounded protecting Shinji' and 06 is destroyed in ep 24 when the final 12 Apostolos vapourize America.


edit- I'm doing a rewatch of the series on the 25th anniversary of each episodes airing (yes you too can be this cool) and had just got to ep 22 and Misato and Hyuga's conversation yesterday. IIRC as it's been a while the conversation about some of the MP Evas specific construction sites like Germany and China happens between Gendo and Fuyutski next episode (or 24?) possibly when viewing the Ashinoko lake created by Eva 00s destruction.

I'm blanking on the exact wording right now, but it is actually left unclear in the dialogue if 05 and 06 were scrapped altogether or just individual parts of them were cut off and sent over for repairs. Make of that whatever you will.

Blockio wrote:I'm blanking on the exact wording right now, but it is actually left unclear in the dialogue if 05 and 06 were scrapped altogether or just individual parts of them were cut off and sent over for repairs. Make of that whatever you will.

Yeah, I was wrong to say 'scrapped'. I just rewatched the Misato Hyuga conversation and they say (paraphrase) -construction begun on Evas up to Unit 13, in seven different locations around the world, and parts sent from Germany from Units 05 and 06 that are under construction there (thought the Japanese might have a slightly different sense?). I assumed because the MP Evas were so different that Eva series 5 and 6 were start overs from the originals. I'm not sure if it's mentioned again in the series the exact number of MP Evas under construction so maybe at this stage in production (of the show that is) they were planning on only having 7 Mp Evas (Units 07-13) instead of the 9 we got in EoE.

As for the relatively speedy manufacture of the MP Evas you could see them, rather than SEELE having spare Eva bodies waiting for S2 engines to be installed, manufacturing the S2 engines first and the Evas being 'grown' rapidly from these cores 9maybe after infusion of the Adam DNA or samples they grew the other Evas from). One of the key abilities of the Angels/S2 engines is to autonomously regenerate themselves. We see Sandalphon grow rapidly from an embryo, and in EoE the MP series heal themselves of damage in a matter of minutes, while in the series a month after Zeruel's attack Unit 02 has to get new arms and a head grafted on from another Eva.

Lacissal wrote:I assumed because the MP Evas were so different that Eva series 5 and 6 were start overs from the originals.

That is my headcanon as well, but the show is a bit mushy on that end, so we can't say for certain; to the extent of my knowledge there also isn't any supplementary material talking about that.

I'm not sure if it's mentioned again in the series the exact number of MP Evas under construction so maybe at this stage in production (of the show that is) they were planning on only having 7 Mp Evas (Units 07-13) instead of the 9 we got in EoE.

Another interesting tidbit, Seele's original plan actually calles for 12 MPEs, but three of them weren't finished in time. It's obviously all a bit contrived, but I do like the numberplay in that.

As for the relatively speedy manufacture of the MP Evas you could see them, rather than SEELE having spare Eva bodies waiting for S2 engines to be installed, manufacturing the S2 engines first and the Evas being 'grown' rapidly from these cores 9maybe after infusion of the Adam DNA or samples they grew the other Evas from). One of the key abilities of the Angels/S2 engines is to autonomously regenerate themselves. We see Sandalphon grow rapidly from an embryo, and in EoE the MP series heal themselves of damage in a matter of minutes, while in the series a month after Zeruel's attack Unit 02 has to get new arms and a head grafted on from another Eva.

I can see that being possible, yeah. I'm a bit too rusty on NGE mechanics to say for certain, but off the top of my head, that does seem plausible

EDIT: Someone pointed out to me that the MPEs don't actually regenerate themselves; more here. I don't think this necessarily stands in the way of the theory on how they are grown, but it is worth keeping in mind

I definitely assumed the MPE’s regenerated solely because of the one that gets conspicuously torn in half but somehow ends up back in one piece later. Looks like that still ends up unexplained but is probably just a continuity error - or the result of merely accelerated healing that’s not on par with the ability to fully regenerate limbs in minutes.

I know Unit-01 was budded off of Lilith, but did we ever find out how the Adam-based Evas were manufactured? Also, in the Eva graveyard we see potentially hundreds (!) of Unit-0 skeletons, seemingly with fully helmeted heads. Why would they throw away money and resources putting helmets on all those failed prototypes anyways?

Blockio wrote: EDIT: Someone pointed out to me that the MPEs don't actually regenerate themselves; more here. I don't think this necessarily stands in the way of the theory on how they are grown, but it is worth keeping in mind

Thank you for the link! On the wiki art from the Groundworks showing which MP Eva is which based off damage:

I just rewatched the scene from EoE where the MP Evas reactivate. I think it's possible to reconcile Reichu's post with the S2 engine having restorative properties. Obvs they don't heal or restore their injuries (in the show Sachiel takes a few hours after getting hit by an N2 mine to recover and grow a new face, not healing the old one but pushing it out the way and Israfel takes a week to restore itself while the MP Eva scene happens over a very short period of time- the others reactivate just after 02's reserve power runs out) but from Asuka and Maya's dialogue ('last one' and 'the defeated Eva series') it's clear that the MP Evas recieved damage that would be critical or incapacitating for a regular Eva unit, such as having your spine wrung like a towel, and we regularly see the Evas in the show laid up for long periods of repair, but from Asuka and Maya's shock at them reactivating, you could assume that the S2 engine allowed them to become functional again in that short time.

Archer wrote:I know Unit-01 was budded off of Lilith, but did we ever find out how the Adam-based Evas were manufactured?

The Classified Information from NGE2 does say 'cloned from the First Angel'. In the show I think they just use phrases like 'born/created from Adam. The scene with probably the most relevant wording would be in Ep 21 in the flashback when Gendo and Akagi's mother show Fuyutski the skeletal Unit 00. There's no clear shots like Unit 00 being grown from Lilith in the Reiquarium sequence so you probably have to assume the Katsuragi expedition took samples from Adam before 2nd Impact, or samples were taken from the Adam embryo whenever it was recovered and the Evas were cultured from that, like how Eve was created around Adam's rib in Genesis.

I had assumed that they were able to reactivate despite their catastrophic damage because they used a Dummy Plug instead of an actual living pilot. The sympathetic feedback from the Evangelion's injuries would leave a living pilot either unconscious or dead. The Dummy Plug can't feel pain, so it would be able to remain combat capable up to the point that the Evangelion itself is totally incapacitated or outright destroyed.