Can I just remodel my town without losing anything?

You cannot reset your town, you can only delete it. This deletes the town, everything and everyone in it, as well as all player characters that reside in the town.

Afterwards you can start your town brand new as if you just bought the game.

You can't reset your town but what you can do is delete it. You lose everything in the town but one of my tricks is for a friend to hold your items and then have them give the items back after you create a new town. You also get randomly new picked residents and you lose relationships with residents and you get a new town fruit.