Good question, it would be a pretty neat feature. It may be possible by adding a 'footprint' emitter to the footsteps tag of the player / AI models. This emitter would be activated by the walking / running animation, at the correct frames (when a foot hits the ground).
This way it may be possible, but their may also be a lot of obstacles I didn't notice
I was looking for another thread i thought this texturre would fit in nicley with. one where people were talking about taking some .map maps and putting them together to make a mod. i'm not sure what the name of it was though.