Omfg, Plot-resetting is the worst. Everyone can agree. You have to have a lot of patience.
Basically, when a new villager is supposed to arrive, instead of going on your mayor, you click new player or whatever. Then after you created a new player, you walk around town looking for a plotted house. If you find it, and don't like the location, you have to exit the game and redo what you just did until you find the perfect spot. If you find they're in the perfect spot, then do the stuff you do when you make a new villager, then after, save and quit and delete the new character.