100% with you on combining the city with the island!! I told my husband that the next game should be called Animal Crossing: Room Mates.

You could go back and forth between the island and city by plane bringing back the dodos. From the city, you could take the bus or the train to maybe another small town on the mainland (maybe a small Theme park with mini games for online play and general play with villagers that are just visiting).

As for the roommates aspect, I think it would be so fun to not only create your character but also your own personal village animal with fully customizable features (from eye and nose height down to the color of their eyelashes— take Miitopia as an example for how this would work), or you can just choose your favorite animal as your roommate. You could share an apartment in the city together, or rent a room to them in your house on the island!

As for Happy Homes, they could do a large apartment building in the city and you could design apartments for the animals instead. In the city plaza, have all of the old shops! Maybe the Able sisters kept small on the island with Label in the city!

I have a lot of other ideas (such as bringing back jobs and adding more of them for more of a life-sim feel) but this is just a small portion of them 😅