I get that, just doesn't work because of the low profile of those things.
What about the venting bit?
Ride a 40kg velomobile up a steep hill (like they do in TCR) and pray for wind?
Depends on the design of the shell, if the bubble canopy is hinged appropriately, the rider could set it ajar. Add a battery-powered fan for low-speed efforts?
I've got an OG Ice Trike (tadpole) which is slow enough without adding the weight of a fairing.
Note "visibility and crumple zones", i.e. people see the vehicle, not you seeing where you're going.