It's not about "changing" it's about "adding". As it stands, all the personalities are pretty one-note. Adding in nuance to how each character interacts with or doesn't willing interact with the feederism kink could go a long way to giving them depth.
See my example I gave concerning the bratty personality. That is the way I envision that specific personality type would engage with the kink if you, the player, were to get them into it via persuasion/them having an unrelated sexual awakening to the kink by accident/circumstance as they see themselves and/or the player getting larger.
You could even have that factor into the gameplay a bit, as perhaps different ladies of the same personality type could have differing reactions to their weight gain and/or the player's weight gain as it occurs. Some of them might not be into the kink at all and actively fight against it and disapprove, some might be SUPER into it in one way or another, and some might not be personally into it, but accepting and enabling the player's kink out of love, either getting fatter for the player or agreeing to be the player's personal feeder.
I find it personally delicious in feeding kink stories when the feeder character is low-key kinda not into it, but enabling the very much into it feedee character, for example.
Thus, say, the anxious personality, for example, would also have a completely different and unique way of interacting with the kink than the other personality types.
So on and so forth for all the personality types. I'm not suggesting for their personalities to be "changeable". I'm suggesting that MORE could be added to them.