My main concern is condensation. Are these vinyl tents vented somehow? Also, what is the purpose of the liner? Added protection from the elements?
You might have hit on an issue right there, and they are vented. I'll tell you what I know about this though. First off, it's waterresistant vinyl...it's gonna sweat! Of the two Command post tents I have, both have been up at the GA rally in a previous year. The one Gimp and I were using had a tarp layed down as a floor (Even though it has a floor piece, I didn't want to use it and get it filthy). During the day it was high 70's or so, at night high 40's low 50's. It was sweating some but not really dripping. The other one that Eric's Uncle Tom was using, we didn't put the floor down either, and it had no tarp. That tent was like a rainforest in it the first night. After that we got some older coleman tent heaters from Phil to use to keep warm, and the condensation in mine was better. The other one was still sweating pretty good, but not as badly.
So, my conclusion is this...Use a floor, or you will be sorry. And some type of dry heat (NOT Propane because it draws moisture) will help the sweating issue.
Another question about the military tents. What stove is used? Are they propane burning stoves? wood burners?
Most of the mil. tent heaters are liquid fuel (diesel/kerosine fired) heaters. Some have a wood/coal conversion. But you can use any tent stove you want as long as the vent will fit through the stack opening. As stated above, I would avoid propane because it draws moisture. That's fine in a canvas tent that can breath, but will be not so good in a vinyl one.