You can make your own ally or villain, just not a Cure. You'd be able to choose Cure Radiant or Illusion from the mains. It's just to prevent people from making a crapload of Cures and no villains or allies.
If there is a real demand for people to make Cures, I might allow one or two as long as they fit the theme of what you're able see (the three Cures cover color, light and movement already), but their roster should be extremely limited. I'm sorry for the constraints, but I don't want an overload of Cures and not having anyone for them to fight or interact with.
Plus I'll move this into Casual if it's better for most folks.