Hmm these aren't really things I really could conceive happening in future game(s) but they're fun to think of.
More control in camera perspective. Basically like when you're inside a house but I want that outdoors too
More villager X villager interaction. The most they do right now is talk to each other sometimes, or gossip, or ask you to run deliveries... I want to
see cute friendships and stuff, like them standing side-by-side fishing or sitting in a cafe together, or them playing hide and seek with each other that we can join in to name some examples. I also want to hear drama~ xD
In HHD I love that they can run around and interact with their environment.
A "neighboring town", kind of like Main street or the Streetpass area but the special characters are here during their off-hours, like you can see Reese's home or Tom Nook's, or play-date with the Nooklings, not just check out their RVs or Resetti's center. You develop friendships with them like villagers. You can't customize this area, it belongs to them. OR more travel like the island; like taking trains to their towns or a plane to wherever Gulliver is (I love him hes hilarious)
An online hub/plaza where you can interact and chat with other players? Similar to how you have a bunch of animals running around main street in HHD. You can choose a server to enter, so you can meet up and hang out with large groups. Idk that might not work well though unless there's a censoring or report feature. Kind of like the island but bigger, and you can easily visit/teleport to others' towns or trade too. Like, with an actual, secure trade feature, not just dropping items in their town
More "Alchemizing" to get certain special items, kind of like how gold nuggets can be used to create gold furniture. Requiring dyes or paint to recolor your furniture and such
When you deep-sea dive, you can actually see underneath the water
I miss the constellation feature so much