Nope I wouldn't consider something that would not benefit performance. You can set your texture to 1/4 and see what kind of gains you might get. It will be minimal unless you have complete potato of a rig which you don't. All the performance loss is from the Unity character controller and the A* pathing over a voxel world. You can drop 1,000 static mesh zombies in a unity scene if you have the time and it will run fine IMO. Turn on 50 unity character controllers (their physics, collision, ragdoll components, skeletons, mechanim controler etc) and pathing and and watch your FPS tank.
I think we've done some optimizing on this front since 17, but it kind of is what it is and without getting unity source and rewritting a stripped down controller we probably won't be seeing a ton of gains.