A coworker of mine researched and said the only vehicle that can "officially" be flat towed with no warranty issues is a Honda Odyssey. Clearly more vehicles then that get flat towed, so either he overlooked something or lots of people are taking risks that they may or may not understand.
I wouldn't risk my 40k investment over trying to save a few dollars. Personally, I wouldn't screw around with a dolly, either. A quick google search found dollies for about $1k and full trailers starting at $2.5k with most around $4k. There's lots of uses for a flat trailer once you have one and there's almost always somewhere you could dump the flat trailer once you've arrived. Plus you could back it up while loaded and rent it out while you're not traveling.
Should you be able to get something rigged up, you could also charge the Bolt from the RV while driving, if your RV keeps the 110V outlets live. Obviously, you would want to use the 8A setting and then only if you really need to charge, but it should work. Definitely not efficient, but feasible.