It's a great start, and I look forward to this project's progression (especially to being seduced by Izumi)!
As far as underrepresented character types go, I'd like to suggest a klutzy girl. It would fit well with the ecchi tone you seem to be going for, and you wouldn't have to overdo it they'd infrequently be on screen. You could even do something like making them some sort of expert like a gymnast or chef (or perhaps a fellow chemist?), but their new booty keeps putting them in situations that make them look amateurish in front of the MC.
I hope this project gets the attention it deserves. Us AE enjoyers are woefully underrepresented in expansion content, and you're doing good work to correct that!