Yes! I love the sounds of this. One big Magical Girl crossover.

In terms of idea pitching, I prefer the melting pot setting where all the canons are together, and I could go either way with Canon villains or OC villains. Same goes for Magical Girl/Boy OC's
Also, what pool of Magical Girl shows would we be dealing with? I would imagine some of the more popular series would be included, like Sailor Moon, Precure, Tokyo Mew Mew, Madoka, etc.