I think I could come up with infinite things, but stuff I can think of right now is I want relationships with villagers being able to move in with you, and on the flipside villagers being able to fall in love with each other and you helping them get together. In general I want more fun and interesting characters and households with more than one villager, so you could have families with kid villagers, roomies etc. You could have a bunch of students living in a collective together, taking the train to college on weekdays and staying up late at night, or a romantic couple who always move around together for example.
Also, more engaging fishing, free camera control and seamless transitions when going inside buildings. In general there's too much loading and listening to the same dialogue over and over again. I want a "cut to the chase"-button after the first time you've listened to it.