This is my process that worked for me:
1. Start with a save with 10 villagers.
2. Open NHSE. Load an empty villager onto one of the villagers. Only one. Save. This is your Save-1.
3. Restore Save-1 on Switch, open up your game, go check if that villager's house had turned into an available plot.
4. If it does turn into available plot, save the game. Quit. Backup that save. Let's call it Save-2.
5. Open Save-2 on NHSE, now edit that empty villager into the one you want, for example, Raymond. Save. This is Save-3.
6. Restore Save-3 on your Switch, open up your game, go to Mystery Island and invite that person to your island.
7. Go back to your island, check that available plot, it should say SOLD with 'Raymond' name instead of that person you invited.
8. Save, quit the game, go to your system and timeskip one day, go back to your game and Raymond should be there with correct house.
Try these and let me know if it works?
