I had the same problem, in a similar sized townhome. My solution was similar to your first option. I bought and installed a wireless thermostat. This was back in the late 2000's, so it predates the "smart" thermostats like the Nest. It's just a basic programmable thermostat you can move around.
It works well enough. In the summer, I can move it upstairs so the upstairs stays cool. In the winter I could move it downstairs, but generally I leave it upstairs anyway because that's where the bedrooms are. I remember the thermostat was a bit pricy back in the day, but I'm still using it some 15 years later so I've gotten my money's worth out of it.