Since you're thinking of expanding the game now, have you considered adding in optional missions? Within the caves they could be to scrounge for additional resources (items, money, whatever) and outside they could be job requests.
I bring this up because there's this RPG called
MercenaryNTR wherein you send out party members to do jobs and NTR events can happen between who you send out. That game sucks otherwise, and even that system is underutilized, but I always thought it was a really interesting way to add an optional NTR mechanic to a game.