At the very least, I think it would be interesting if being a (metaphorical) whale to them and buying up their content caused their weight gain to speed up due to you effectively funding their gluttonous lifestyle.
As it is currently, I have a new save that I made for this update that's been going on for over 800 in game days and the top model on that save still hasn't moved from severely fat (where she started) to barely mobile. It's so incredibly slow and full of nothing that the models aside from the girls you have model and/or your own character might as well not exist.
I also definitely agree that it would be cool to be able to meet them, date them, or otherwise influence their gains in person.