Even though you can't put up a mast and are currently isolated from the rest of the mesh, put up a node anyway, and then add yourself to one of the maps with, say, a quarter mile of inaccuracy.

If somebody was to drive to the location you have your node pinned at, with a quarter mile of inaccuracy, they would still be able to communicate with your node.

A node on a mast is great. A node on your roof is good. So, if you can't have great, don't let perfect be the enemy of the good and put up a node on your roof. Your house is still probably around 30 feet tall, so that's still 30 feet of height, and somebody will eventually be able to communicate with you.

Otherwise, you get the chicken and egg problem, where a new person turns on a mesh core node and sees nobody available, so they turn off their mesh core node and put it in a drawer, and when their neighbor gets a mesh core node and turns it on, they see nobody there, so they turn off their mesh core node and put it in a drawer, not knowing that their neighbor has one, and if they had just left it on, they would have someone to communicate with.

As for the government making their own client and trying to hunt people down, you can make mesh nodes out of a lot of things because it's so small and low-powered. I've seen people make security cameras into mesh nodes or solar lights into mesh nodes and when you mentioned this my thought went to a mesh teddy bear. I've never seen anybody create a mesh teddy bear, but I don't see why you couldn't.