I agree that there are a lot of ways you can approach fixing whats broke. One way is to bring in an experienced and proven PG to provide leadership on the floor. Calderon is someone that can do that. I also agree that moving Tyreke back to PG, and drafting McLemore, a very talented player that can kill the other team offensively, but can also be a dominating defensive player is another approach. I can see the benefits of both ways, but honestly can't tell you which way is the best way. I suspect that short term, the Calderon approach is the best, but long term the McLemore, or plug in Oladipo, approach might be the best.
But, if you leave Tyreke at SG, then defensively having IT as the starting PG makes you very vunerable. Not for lack of effort on his part, but because a smart team with a Derron Williams or any smart 6'2" or over PG is going to post him up and break down the defense when the help comes. And I'm talking about the playoffs now. Run and gun never works in the playoffs when teams become serious about winning.