If I could only pick ONE big thing, it would have to be fleshing out all the NPCs. Give them more dialogue, heart events, and general character development. I'd also love to see the stationary and unbefriendable characters be freed. What I mean by that is giving them things to do in town. Let them have a life outside of the one place they stand every day. Gunther never leaves the library, and he isn't even seen at festivals. Even Marlon shows up to festivals, but even still, it's odd that Gil never shows up with him. Give them their own birthdays, let us talk to them and give them presents, let them go to the movies with us, let them go to festivals, let them do things in town, let them show up to our wedding, let us befriend them! Along with them, maybe Hat Mouse, Mr. Qi, and Morris (if that's what you really want) as well? More mailbox quests could be another way to give NPCs character, along with giving the player more things to do, as well as ways to increase friendship and get gold. I especially hope to see Dwarf content, seeing what we got with Krobus.