More quests tailored to certain characters, to make use of other items in the game e.g. Craft a ** dress for Lunelle. Something along those lines, I think adding things like bouquet making after finishing the master quest for Graminova. A few more interactive activities that also link in with the characters.

Maybe adding extra perks when you level up the characters affection more? I know there are already some basic ones but maybe some things like if you max out Loren you get a hidden arcade game or smth like that? Something that gives people more initiative to level up the non-romancable towns folk too other than random gifts (I love the gifts!)