...had a silly mental image today when my mind remembered Shinji and WH40k
from years past:
Lulz, and I was just thinking about that crazy fic!
Man, that was quite an experience.
By the way, you should change Shinji to Shinjiko for this fic
It wouldn't be an instant characterization change, but a gradual one. Shinji's initial personality is kept, it's only the progression that's altered. Plus I thought it'd be funny if Asuka was Shinji's oneesama and the first time Shinji calls her as such, Asuka pauses... then goes "that's right, I am your better and it's a good thing you recognize the fact".
Though their relationship is less senpai/kouhai (though Shinji does think of Asuka as a senpai when it comes to piloting and pushes herself hard specifically to get her approval) and more "Shinji randomly going fucking nuts and Asuka pushing herself even harder to not fall behind".
This is a very interesting idea. The image of Shinjiko turning into Noriko and calling out Gunbuster attacks is a hard one to beat.
You've piqued my curiosity, sir. Go ahead!