I voted for Sim Aloo, mostly because I'm still holding out hope for modern versions of each of the Vintage figures and it'd be great if we could finally cross him off the list.
I'm like Rob - I asked the same question - "who the heck is Doctor Aphra?!?!" - but I guess if she were to win that would be at least a new character that's never been made before.
Fives seems like a weird choice, I guess I'm not remembering him very well - did we never get a version of him in the Clone Wars line? Seems like an odd choice really, especially since if he were to come out in the Vintage line, I doubt they would do him in the style of the Clone Wars figures.
I would have hoped that The Emperor and Ahsoka would be dead last as we really don't need new versions of either of them. Yak Face has been done before and definitely needs a re-do, but I'd be shocked if he wasn't already "on deck" for a return of the Vintage line already.
Kinda a shame that there aren't any members of the Ghost Crew on here. While I'm not a fan of the 6" line, I do like what they've done with Kanan, Sabine and Hera. Considering that Disney Parks just gave us what is essentially a definitive, Vintage-esque version of Chopper, I think it would be great if the Vintage line featured "realistic" versions of the rest of the Ghost crew.