I agree, I don't think he'll ever be James Harden but I don't think you're ever going to see him as just a point guard either. He will always play both positions for us and while I agree he was worn down at times having to do too much, IMO it was more because he didn't have an effective running mate.
Pair him with a good combo guard and I'll be happy and so will Booker. Sure, I'd love to have the next Steve Nash out there but I'm quite positive that even Steve Nash would be playing more like a combo guard in today's game. As I've mentioned many times, the refs give breaks to the perimeter shooters and ball handlers that they don't extend to any other position, it would be shortsighted to not allow Booker to benefit from that protection.
We don't need another Steve Nash, but we at LEAST need someone who is more capable than Booker playing the point and who can show the way to whoever ends up as our point guard of the future. In no universe is Tyler Johnson that player.