As much as I like minimizing components, I think having separate exhaust and air assist is the way to go, you really don't want to be pushing the exhaust gasses over the lens.
I do have to find a better air assist than my Hitachi twin stack compressor, not only is it loud, but as I was trying to cut a vent adaptor it tripped the breaker and shutdown the cutter and exhaust. My own fault for plugging everything in to the same circuit knowing that damn thing draws a lot of amps when it kicks in...