Proper clothing works for me. I doubt a heater would work very well in a treestand.
Ha it's good to see another weirdo like me. I hate sitting in a box. A few layers of merino wool and I can sit wherever I need to and see and sense everything around me. No eating popcorn drinking out of my yeti tumbler. I mostly just bowhunt but if I feel like gun hunting I park a varmint chair on a bluff.
To add to the post my brother hunts boxes and has put a little buddy in each blind. Then he only has to pack a propain bottle in with him. Be very careful whenever you light them. Take your ear plugs out. You've got to be able to hear. Turn your nose on high also. Watch for mirage effect from fumes. Do all this before you light it. My brother has so many story's. My favorite it the time he lite it and the whole floor of the blind glowed blue. He's lucky he's never been hurt. He's built a little stand in the corner of each blind which is a great idea cause it keeps it off the ground and prevents tipping.