A body-type preference system could definitely be interesting. Some girls might encourage you to gain weight, whilst others might start shaming you for getting too fat.
I may well add that as the default mode (if player weight gain is enabled), but if I do, I think I'll add some options to help customise it if desired. Perhaps:
- Toggle between all girls prefer fat/all prefer thin/random mixture/no preference.
- Mode where the girls don't gain weight at all.
So for example you could set these options to have a game where the girls are all slim feeders who encourage the player to gain weight. Or a mutual gaining game. Or a game on hard mode where you really have to maximise your affection gains to keep the girls interested.
What do you think?