One point about Carl Landry. I prefer Landry over JT as third big off the bench. Assume your rotation is 1. Cousins, 2. Defensive big, 3. Landry, 4. Hustle roleplayer for spot minutes. Cousins and Defensive big get the bulk of minutes with Landry filling in when we need scoring off the bench. Landry can play with either Cousins (to shore up Landry's lack of rebounding) or Defensive Big (assuming Defensive big is bigger than Josh Smith). Landry's post game is more polished than Cousins, and Cousins has a better jumper now than when he played with Landry last. I think the tandem can work on offense.
If you look at this team from last year, we often lost games in the second quarter and late in the third when our bench was just generally unable to score. That is largely on Smart, but the personnel is a problem too. Smart ran lineups like Jimmer, Salmons, James Johnson, T-Rob, Hayes at opponents pretty frequently. Of those players, only Jimmer and Salmons had any hope of doing anything offensively, and usually from distance, and neither of them were great at creating for themselves or others.
If you're running jumpshooting offense in the half-court, you end up putting up contested shots, and you need rebounding to clean up the misses. T-Rob and Hayes just got outsized by opponent bench bigs.
Alternatively, if you run offense out of the post in the half-court, your jumpshots can come off kickouts and your bigs are also generally in better rebounding position (less dependent on setting picks for their guards.) It also leads to rebounds beneath the basket which slows down opponents trying to push you in transition, and shores up defense at the other end. Oh, and bigs who play in the post get fouled, which also slows pace and leads to less transition opportunities for opponents. If we can't have Tyreke scoring at the rim, we need to pound the ball down opponents throats through whatever means available, and a reliable post scorer off the bench fits that need as well as anything.
The missing piece to the Landry puzzle is obviously a defensive big to start. Whether we can pick one up through trade remains to be seen.