Great comments, guys. Glad to see there's interest, even if my actual player base might be really small. I've also thought about pulling Black Cat (have to play the mod first to see how good it is) from the lineup, which would fill all 34 slots.
Can we mod the 360 version? That is the version of the game I started with and I really enjoy playing from my couch instead of my computer desk.
Yes, but the console itself has to be modified, too. I got a RGH modded console (it dual boots to retail/modded modes) in exchange for some PC repair work I did.
I would suggest Psylocke for the secret slot. She's a scantily-clad psychic ninja, she's a bad-ass, and if you team her with Wolverine, Deadpool, and Nightcrawler (AoA X-Force skin), you have Uncanny X-Force, which can be a team bonus.
I have a 360, but didn't JTAG it. This is an interesting project. Good luck with that.
I thought about Psylocke, but it's yet another one of the X-Men, and with Gambit and Rogue (as a Ms. Marvel costume) I've got 7 already. I figured someone non-mutant and non-Avenger might balance things out. That's why I lean toward Namor. He's been affiliated with the X-Men, Fantastic Four and Avengers, but is no longer really a big part of any.
For the last slot, I like both Captain Marvel and Namor. It's tough to choose between them. There's so many others -- did you consider Vision, Giant Man, Wasp, Black Bolt, or Angel?
Angel was really the only one I had considered. I'm big on not breaking the story, which is why Hulk unlocks after Omega Base, Nightcrawler would get a story fix, Cyclops too, etc. Vision has so many spoken lines and plays a pretty big part in the game, otherwise I'd use him. Namor effectively disappears after Atlantis, meaning he could unlock at some point during that mission or after.