Honest question. How come you are only willing to include players that are his height or 4 inches shorter than him? He is 6'4 and pretty built (not like he is fat by any stretch). He also certainly does not play small.
Answer: I view Smart as a combo guard, and if you want to find players slotted into that role, you're going to be looking at guys in that size range.
Certainly there are larger guys playing at that position, but I think when you start looking at players listed 6'5'', 6'6'', 6'7'', you start to get guys who had some advantages in terms of seeing the floor and shooting over guys that Smart simply will never have, no matter how much muscle he puts on.
Even so, I did a search setting aside height restrictions and looking only at guys with an AST% > 15.
The only notable new name that came up was Alexey Shved.
The thing is, most of the bigger guys tend to get to the line more often than they jack a three pointer. That's very much not the case with Smart (5.4 3PA / 36 compared to 2.9 FTA / 36).
Smart's size is a nice feature, especially on defense, but he hasn't really used it to add much to his offensive game.
As for your comment re: Bradley, I stand by what I said previously. AB to me was a raw player who has improved leaps and bounds since he came into the league and demonstrated gradual improvement, with some noted struggles due to injuries and a necessary increase in offensive workload.
Smart is a different story to me. That's not to say he hasn't improved, but to me most of the improvement I've seen has been mental / decisionmaking. He's not adding huge pieces to his game that weren't there before.