I've seen several suggestions for feminine pc already, but I'll also suggest it.
I understand that you'd like to retain the whole femboy survival theme so i propose like previoius user suggested that the slime enemy can feminize you if you keep getting caught by them, I also think a debuff where slime are inside you slowing you down or even controlling your movement for you to get caught by the enemy, which would trigger a quick time event or something which i think is pretty cool.
I also think it would be pretty cool if the pc could manually buy these transformations from a shop, and it could give them maybe a stat change, something something+ something something- per feminisation.
Also new clothes would be nice.
(Excuse me if some of these were already added or if i got something wrong I haven't played in a while)