I group Carr, with the Rivers and Ryan tier of QBs. QB's that are good, franchise guys, but unless every other element of the team is elite, you are not going to win things with them. Perhaps most QB's are like that and the haters on here will with legitimacy say that's the ceiling for Tua but my question would be: Why bother?
I have heard people wanting to trade for Cousins, or bring in a Jimmy G, give Tua some competition, but again what is the point of that ? Say, Tua can't beat the guy out, you are then stuck with a middle of the road QB where sneaking into the playoffs is your ceiling pretty much where we are now with our young QB developing. Personally just stick with what we have and build around him, give him the chance to prove he is or not more than a middle of the road guy. Save resources you used to acquire this other QB, to buy that vet lineman or draft that WR or stud RB.