Rayve - I know there are plenty of Canadian heroes, eh... but Wolverine's the baddest of the bad, and the deepest of all of the X-Men, plus he gets all the hotties...
Natalie - Straying into the realm of pulp and other fiction muddies the waters quite a bit, perhaps too much to make some kind of coherant plot... which of course is the problem with a DC/Marvel crossover as well, so Batman'd be out for me...
Darwishi - Crossover's can be a sticky issue, aye, but if canon characters are going to be allowed, there shouldn't be a restriction to who can be played, at least in my mind's eye. I've other possibilities, though... Iceman's always been a favorite... or hell, if I'm gonna get kinky, Multiple Man's a riot... and Nightcrawler, well, yeah...
...'course I could just pull out an original... Thom Payne, or Flagwaver maybe...
Monkey - Mmm, power charged by arrousal... hate to see her lover's hair after a shattering orgasm...