If anyone has ever played The Sims Medieval wouldnt it be cool to have that in THE SIMS 4? Dragons, Fairies, Elves, Gargoyles, Horses, Kings/Queens, Masons & Unicorns.
They could make it like in Batuu where everyone gets dressed in character clothes, so even if Nancy or Judith show up they would be dressed in medieval clothing. Similarly, they could make it so they either couldn't leave the medieval neighbourhood or they would change their clothing to modern one when they visit regular neighbourhoods. I also like the idea of a medieval fair, but maybe it could last longer than a few hours.