When printing some filaments like ABS, you do not generally want cooling because it makes prints warp and layers delaminate. Layers with overhang (in particular ones with curves or angles in the overhang) are almost impossible to print without some cooling. I would suggest another fan override in the cooling section where one could specify a fan power to be applied only to layers that included an overhang that exceeded a configurable angle. For example, turn the fan on to 10% for layers that include an overhang of 40% or worse. I would expect that Simplify3D knows the overhang percent for each layer, so that this should be possible. Right now, it would be necessary to create different processes, based on trying to figure out which layers do or do not have overhangs that require cooling.