Well, perhaps he's the "Super Unlockable" seeing as I saw that list of files and his was the only one that we haven't seen as far as characters go. Though whether he is or not doesn't matter as I never cared for Jax myself but meh, more characters can't be a bad thing I guess.

Liu Kang and Raiden. Why would they be missing from the i-Guide if they weren't?

Yeah, I think there are not more than 24 characters in the game...