Yo! I came up with the idea for two hero team-ups. I thought it would be easier on creators who could split duties between writing and art. Not sure how three would work in that case but if you're planning to arrange creative teams then I guess it's not a problem. I like the idea so far. It reminds me of a lot of Secret Wars, but with a focus on multiple teams.
I'll admit I got a little confused with the QUEEN and ROOK parts. Maybe it's stuff from your comic I'm not familiar with but when you started taking about dragoons and bishops I was like "..........what...". I like the idea of Checkmate as the main baddie with a team of villains from other comics. If the QUEEN section is just cannon-fodder goons for the heroes beat up quickly before the real villains, that's fine. It just became a little too much for me personally.
Also I'm no lawyer but on the CC discussion, when we share our characters around it would be for this crossover only. If a character that's not under CC appears in a CC comic I don't think that would make the non-CC character a CC one. The creator is allowing use for this special circumstance only. It's the same principle of how we can use other characters in our comic during the crossover but not after. (Again, I could be talking out my ass right now.)
Also also, when/where can we submit characters. I would like to join in.