Congrats on your decision to go aluminum shack. That should last for many years.
I agree too, wood is a pain. Reminds me of the days fishing with my grandfather as a kid. Of course I had to be the one to haul out the wood for the stove, he didn't own a sled or a toboggan, just me.
I love heating with Propane. Very easy and easy to adjust the temperature. I have a propane cook stove that we run for heat / cooking. Dual purpose.
I also know someone with a vent less wall mount propane heater like the one your asking about. I heard that they had some problems with their heater not starting, not sure if it was due to the cold or something else was the problem. I think they eventually either figured it out or got a new heater to replace the one they had. I'll have to ask them and advise later.
There's some special plumbing you will need to do in addition to running copper to and from your heater ie: condensation trap will need to be built...not a big deal but not included with the heater.
Some heaters require more than that of a 20lb propane tank, something to look into as some recommend 100lbs tanks. Depending on the size of your shack, either go with the 10k btu or 20k btu heater. Check them out on Northern Tools.com
Not sure I understand your comment about "if you go with a heater that does not require juice, you don't need to use your generator all the time"....do you mean for a blower? Again, depending on the size of your shack, you might not need a blower.
Another thought to think about is to go with a Blue Flame heater and not a IR heater which will heat up objects instead of the air.....blue flame heats the air, IR heats objects and gets zorching hot. A blue flame might take longer to heat up the shack but it will be more controllable in terms of regulating the heat.
Good luck! Hope this helps.