Really just came to me after fighting with cooling profiles in the slicer. I figured there has to be another way. No idea if that's a better one. Likely not.
As for the benefit, I guess I've just found layer adhesion and warping issues on small details because the print head is spending a lot of time in one area and it seems to cool off more than wanted. The slicer is only going by layer time.
In Cura you can force a fan speed at a layer height. I haven't checked yet but maybe you could use an infill mesh to modify fan speed in a section of the model.
I know the real solution is going to be in the slicer rather than firmware.