I'd love to have some kind of toggleable mechanic - perks, equipment, something like that - that outright prevent certain body parts from having their size changed. I have severe top dysphoria, and it really doesn't play well with scenes that pull stunts like "automatically growing my PC's breasts without warning or consent". It would also be useful in a lot of other cases - say, if someone wants to use the Pink Egg to enhance their PC's feminine assets without shrinking her dick in the process.
Relatedly, and much simpler: warnings for scenes and items (e.g. the Witch's Corset) that cause involuntary TFs. TiTS has this feature, and although the warnings aren't as specific as they ought to be, it's still extremely helpful in letting me avoid unpleasant content.
Another thing that would be really nice is a binder option for underclothes - something that causes your chest to act as flat no matter what the actual size is. 'Cause sometimes you don't want to get rid of your PC's breasts altogether, but you don't necessarily want them taking effect in certain scenes.