I love the game and I've been following it since the beginning of development and I've already seen all the endings, but there's one thing I'd like and that is that it's not just "the end" but that the transformation of the endings is something permanent and can affect the story of the game, maybe we can even talk to Katherine and complain to her, which would cause an event where she takes us to the "friend" who gave her the item "this character is only mentioned after the competition for the size of tits" and then we could be given the option to return to normal or keep the transformation that the item gave us. The transformation of the object of Katherine's competition could perhaps even trigger some events in the city like having a secondary job or participating in some competitions or activities "and that way you can give utility to the city"
I was going to put the examples but nothing occurred to me, instead I thought of something else.
You could add a statistics tab that you should deal with depending on your physique: if you are muscular you may need to go to the gym and stay in shape. If you are obese you may need to eat to keep your stomach full and not go hungry. If you have a big butt or gigantic boobs you may need to buy some special clothes or try to get used to the disproportionate weight of your body so it stops affecting your balance.
For Katherine's competition item transformations the only thing I can think of is that when you become a Cow Girl you have a milk percentage statistic and you have to milk it because if it exceeds 100% first the protagonist will start to complain and at 110% it will start to leak until at 150% she can't hold it anymore and her milk will inevitably spill, maybe you can add items "which would be bought in a supermarket" that can help with the milk thing "in the supermarket the aforementioned clothes would be bought in addition to other accessories."
If you don't mind you could add a dairy factory in the city where you can sell the protagonist's milk and earn money, you could also add a cafeteria where you could eat to satisfy your hunger stat for when you choose to gain weight and an eating contest tab right there where you can earn money and satisfy your hunger at the same time, you could also add a gym for when you decide to get muscular, and for when you improve your butt I don't know what you could add "unless you want to add a night club or something else I don't know what could be added to the butt section"