I sometimes sleep at home my feet sticking out of the down quilt we use because they would be hot otherwise. I sometimes unzip the bottom of the zipper in a traditional sleeping bag because I'm too hot but not so not that I want to throw back the whole thing. In a UL vein, one way to view each of those situations is that I have too much insulation and that there is an opportunity to cut some weight.
People go back and forth on vapor barriers (while sleeping and while awake) and increasingly I'm thinking:
1) there's some metabolism / exertion / insulation balance that reduces sweating
2) my body always gives off some moisture
3) do I just need a certain amount of air flow to carry away that moisture?
On point 3, when I specify ventilation for a building, there's a minimum air flow to maintain good indoor air quality. Moving fresh air through is easier than running a dehumifier (an option we don't have BPing anyway).
Are you thinking this would let you cool off while not admitting any bugs? Or are you thinking of it more to provide ventilation throughout the bag?