Not sure how it would keep the bugs out.
They sell a bug screen/floor for both the Megas and the Betas. If you want something smaller and lighter, look at the Betalight. Two trekking poles, sleeps two people pretty okay, very light.
I believe it won't- the cooling the canister experiences is due to the adiabatic effect of the gas escaping from within, and the inside pressure decreasing. Cooling due to air contact is relatively insignificant. I think a heat exchanger is the way to go, although it sounds kind of scary. People have talked about homemade heat exchangers on this site before.
...nothing?
If you're only on glaciers you just don't need the second rope.
If you're crossing the glacier to get to a rock climb it's a perfectly good plan.