While I like this idea, I do believe that the insurance company will be happy to consider this fraud then when they cancel your coverage it'll even tougher to find coverage.
How is it fraud, your friend rents you a room and you just spend alot of time on the road working, 6 months at a time, as a freelance consultant.
Simple rental agreement, phone, electric bill, heck even put that address on your drivers license, just do not say "I live in a bus", instead say " I like to travel more than the average person". If your friend agrees, no fraud cause you do get mail there and you do pay utilities there.
In Florida people use mail box addresses all the time, especially law enforcement in order to mask the private info from data brokers and the bad guys. statute allows them to mask their private home address from public records but makes no mention about using mailbox addresses so technically it is not illegal to do, in Florida.
There is no law in any state that says you must own a home or that you must rent a home and it must be in your name. What if it was in your girlfriends name or your uncle's name?
Look up your state driver licensing laws regarding how to show proof of residency and start from there!
South Dakota
All applicants are required to provide two documents proving your residential/physical address. These documents must show your full name, your physical/residential address, and be less than one year old. Examples of such documents are a utility bill, a pay stub, a rent receipt, a phone bill, a bank statement, a mortgage document, a homeowner's insurance policy/bill, a tax document, your vehicle registration, etc.