I'm probably in the minority here but I'd prefer that he forgo adding a new character and instead focus on fleshing out the current ones for a while. Outside of maybe Rogue, each girl has probably a single MS document page worth of unique dialogue. Giving them unique dates, study sessions, classroom interactions, and actual conversations would go a long way towards making them feel more like characters and less like a collection of stats to raise.
The relationship system could also use a lot of work. Having a girl go from declaring her undying love for you in one conversation and then the next time you speak with her having her go "I know we're not serious or anything, so wanna be casual sex friends?" is goofy and nonsensical, and has been a problem for like... years now.