I haven't read the whole thread yet, but I've "gotta say what I gotta say before I forget what I wanna say." On the shed idea. I think it's a great solution IF -- and I say IF- because it needs to be insulated and some sort of climate control needs to be addressed. Humidity will ruin your fabric as well as your machine. My DH bought a little metal shed type building and his friend helped him to insulate it and put inexpensive paneling on the walls. He's got a TV and a fridge with an icemaker in there. It's where we keep our various electric skillets, etc. The little 110 AC unit keeps it cool int he warm/hot months and a little electric heater with a thermostat prevents it from getting too cold on those very few cold days that we have down here near the gulf.
I must say that as our family was growing, my sewing space moved from place to place (a tiny corner in our bedroom, a space in the utility room, the dining area and finally in a vacated girls' bedroom. That is the room that is so full that I need to move out to do my quilting. So I move back to the dining area again.
Have machine will travel.
Edit: Oops forgot to say why he bought the shed (which he calls "my building."). He likes to tinker on repairing all sorts of things. It's a place to store our large kitchen things like gumbo pots, pots with burners, etc. plus he keeps all of his tools and guyu things like the weedeaters, blowers, etc. And of course -- the TV. When all of the grandkids are here, he can watch his ballgames in peace out there.