I don't understand your statement that MH are wasted space for 2 people - we found quite the opposite- the higher end you went the more tailored they are for 2 people. The entry levels are typically the bunk houses, sleep 10, etc.
I would never predicate a 2 year journey on having to gut and rebuild a motorhome unless you really just have nothing else to do. A) It would take me 10 years to finish that kind of project, B) when I was done I would have a MH that only I liked and I could never sell it because no one else liked it :)