Yes, I can see your problem. Open water black tank pumping is only legal in the Ohio River or on the ocean past the 12 mile limit. Illegal on a lake or any closed body of water. My boat that I had on Flathead Lake, there was no a/c either. It would have required either the engine or the generator to operate it. Or massive battery bank. Neither of which was appealing - besides the enourmous cost.
Your boat is insulated at the factory. Fiberglass on a boat is far thicker than any rv you'll find. If you need extra, you can buy foam boards - pink with silver covering and glue it to the hull. It held up rather well on my boat.
As to the liveability a 27ft boat is wider than most travel trailers. You don't need a truck to haul it around, b/c the marina does that for you.
Most gas trucks when hauling don't get really good mileage. My SRT-10 got 9.5mpg with a 20,000 trailer.
If you want a travel trailer then rent one to see if it fits your needs, before you purchase.
