I think Cody Zeller would be the perfect fit as our 4-5th big man. He's always been miscast as the lead big man. He's not that. He's a tough role player than knows how to play the right way. He sets good screens, rolls well, and is a good team defender.
He's a guy that could be a reasonable facsimile to Al Horford for a few minutes here or there at center.
On top of that, I think he could be had for a minimum deal.