Go watch some off-screen footage of the character select screen (like at PAX or Gamescom) and you'll notice that Heichachi's title does not include his last name of "Mishima." However, Nathan Drake's title does include his last name of, well, "Drake." Could this mean that Nathan Hale is the Resistance rep for PSABR? Since they share the same first name and the evidence stated above, I believe this leads to the highly plausible conclusion of having Nathan Hale in the game. What are your thoughts?
As much as I hope that this isn't the case, you do make a good point. The only thing I could think of is that "Heihachi Mishima" exceeds the character limit for the title screen. That, or since those are earlier builds, it has changed to include Heihachi's full name.
Why would Heihachi just be "Heihachi" but Drake be "Nathan Drake"?
Because nobody calls Heihachi by his full name and nobody will remember that, while Nathan Drake is referd to both as Nathan and Drake so people wont get cofused.
'Heihachi' is easier for the English-speaking audience to remember than 'Heihachi Mishima' which may be overwhelming (for the people who aren't familiar with him)