I'm going with Mo Williams, just because I think that dude should have spent his whole career playing with LeBron . . . he just seems like exactly the kind of point guard that will look really good playing off Bron. Kyrie is kind of a rich-man's version of Mo.
With Kyrie and Mo, the Cavs can have 48 minutes of that kind of play at the point guard position, and sometimes they can play both.