I'll probablyuse the contests for the Hoenn minigame, just need to figure out what exactly to do with them.
The tunnels make sense for Sinnoh, I was thinking the dance hall for Unova
True, not a lot of legendaries to compete in it at this stage in the journey. Not to mention that it'll be hard to turn it into a series of mini-games. But if there must be pokemon to fuck there, you could always have some fighting type pokemon competing there. Just need to complete their challenge, before you could fuck them.