Anyway, it looks like the general purpose card (with the question mark) is categorized separately from the character cards on the manual, so that almost certainly means that the character cards will have unique purposes (probably an AR game for each one).
The only reason I can think of that would require unique AR cards is if two or more of them interacted.
You're absolutely right! This would be a HUGE opportunity for them to resell their Pokemon cards. The game could just be you seeing your pokemon battle another pokemon off in the distance (maybe someone online!). Think Pokemon Battle Revolution using your 3DS camera and AR-Poke cards. Yeah!
Yeah, it's been confirmed. Each character card brings out the respective game character in the 'real world'. Of course, it's up to the specific game to decide how to use the characters. But having unique cards means that multiple cards can be used with the same camera, and regardless of where you place them, they would still be able to distinguish each character from one another.