An acquaintance of mine bought an old school bus to convert to live in. He specifically chose a school bus, he said, because the states impose stricter requirements on school bus construction than on regular vans and RVs. He wanted the real steel to base his new home on, and he says he got it.
Everything is a compromise, so you have to know what you're giving up and what you're getting. His point of view was that he wanted serious construction for his RV converstion, so he went with the bus. If you get what you need from a bus that you don't get from other vehicles, then your decision is made.