queen carbon
I think that aesthetically, I feel that the human turrets could be made to feel more powerful by being somewhat larger, particularly the AA turret (and perhaps it gets larger missiles). No real buffs for the turrets (although a battleship sized turret does sound cool).
Additionally, I think with the possible alien turret rework rumored, the alien turrets could also be made larger as right now it can often feel like as a human I am getting shot out of nowhere. It is doubly aggravating when the hive spire is firing at you, which has the never ending, perfectly accurate inescapble projectiles which makes it less fun to place against.
humble bison
brittle bough
molten temple