Everyone is going to have a genny and most will probably be running at night. What if I built a plywood box for it with some 1" foam insulation as a sound insulator - would that cut the noise enough to make it worth the effort?
Well the weather is on your side ! People who have done this and run during summer have to use a big fan and a big exhaust vent which lets out a lot of noise.
Forget the plywood. Use 2" foil faced foam. Better, use 2 - 1" sheets glued so that the foil is on both the inside and the outside. You want at least 12" of air space all around the generator. On the side where the exhaust exits, mount a heavy gauge sheet metal plate inside the box, with about a 6" air gap between it and the foam so that the exhaust hits it first. Weld a 90° elbow on the muffler so that the exhaust exits straight down and close to the ground.
Build it with legs so that there is about a 6" air gap at the bottom all the way arround. I would make the next 6" up removeable just in case things got too hot. Air and exhaust will get in/out, but noise does not like to go down and then back up. This is definitely an "experiment". Maybe use a BBQ grill thermometer to monitor temperature inside
Something else to consider is a remote fuel tank.
(Getting your fuel hot is NOT a good idea !) Many generators already have a vacuum operated fuel pump on them. Run your hose from the pump inlet outside the box to a gas can. You can use a standard gas can because there is a pump so you don't have to worry about gravity feed. If there is no fuel pump, you can add one pretty easily.
You are still going to use lots of fuel !!
If I went the BB route and popped a roof vent (both are stuffed with insulation right now), installed a CO detector, how confident could I be that we'll wake up the next morning?
That is the reason you have a CO detector ! A CO2 detector is also a good idea ! Test both every evening. Carry spare batteries, Some batteries don't work well in extremely cold weather.
I've noticed a distinct preference for the oil filled radiant heaters. Why those in particular and why the oil-filled over the quartz radiant that can be mounted up nr the ceiling, out of the way?
Because they give gentle, even heat. Downside is, they don't react quick to a big temp change
(open door). Depending on how the cots are spaced, you are probably going to need 2 of them. A cheap, fan forced "milk house" heater is also a good backup. A 5000 watt genny should run all 3 if needed.
Use a separate 12 gauge extension cords for each heater.
I would very much like to located an old TT to scavenge parts such as the furnace. Are the tent trailer furnaces easily adapted? I'd probably run it down the side of my trailer but the venting on the tent trailer furnace looks like it comes out the end. Possivle to bend that to breathe from the trailer side?
Actually I would look for a good, used direct vent, propane wall furnace, like from a cabin.
If you are going electric,
don't forget the mattress pad warmers !!