Tbh I think Bradley isn't stuck between positions, he's so good on D that him guarding KD wouldn't be a mismatch
As much as I love AB, you are dead wrong here.
Bradley's biggest deficiency for his height was that he could never be the primary ball handler. He can't run the pick-n-roll credibly (can't attack the paint / finish / draw fouls enough). seeroy is exactly right - and this is why Marcus Smart, who is a considerably worse shooter than AB, is still a better "guard" in Brad's system than Avery. Marcus can distribute, handle, assist, and can get to the rim (he just can't convert). He also can defend the 6'8" 3/4s better than Avery.