I have been thinking and a League-esque RPG would be fun. My idea is this:
The time would be from the 1880's to the early 1920's. You could play a character from any book, movie, or show from that time period. As well as playing those, you can also play as real historical people from that era. Of course, you could fictionalize them to fit them into the action. Like have Anastasia really turn up alive and be part of the League like aspect of the game.
The game would not be set in a particular time, just that period. This would allow more characters to become playable. Also, the historical aspects would need to monitored because you couldn't have too large of an event mixing with something that happened years earlier.