You need at least 2' of overhang off the rear of the bed to get a built generator. Some people despise Onan, but I have had good luck with their generators and use mine often.
I prefer a dark place to sleep that is well insulated from temperatures and noises, so I avoid the large Heki skylights, front cab over windows and single pane windows. We also have a full wall wardrobe on one side so there is only one side window/escape hatch. Ventilation is provided by the window and a Fantastic Fan at the foot of the bed.
Northstar makes well insulated campers without slides. Arctic Fox has a limited run 865 they make every year with no slide. If you look at the better 4-season campers you could expand your search to campers with slides. Ours does well with the slide open in cold weather that we can always close if it really got cold.
