My suggestions:
Look for more gears. For Ford that means the TorqueShift Transmission, or Allison on a GM. The TorqueShift can be ID'd by an extra "3" in the shift selector, or the presence of a "Tow/Haul" button instead of an O/D.
A lot of people like Class A. I like the safety features of a Class C cab, and more impertinently, factory wiring up front. The wiring in most Class A's, which includes all dash wiring, is pretty atrocious.
Weigh it. A lot of RVs have little to no capacity on the rear axle. On that note - a longer wheelbase is better for a given layout. Keeps more weight up front which helps with drivability.