For western heroes I thinking of playing Virgil Hawkins/Static or Miles Morales as far as comic book characters go. As a cartoon character I was also thinking Jake Long the American Dragon.

I'm more familiar with anime/manga so for the east I can throw out a few possibilities. Before I do, however, I was wondering about the definite limitations for the selection of characters. For instance, to what extent will non-humanoid characters be able to fit into the setting if any? Are there any restrictions on more "fantastical" characters and elements in this modern setting? Thirdly, in (somewhat) relation to the Darth Vader inquiry, I was wondering about introducing Megatron as a western villain but was not entirely sure if that would be acceptable given his status as the leader of the Decepticons. 

I have other ideas but they're pending at the moment.