I spent some time looking through Title 27 - Transportation in the Arkansas Code.
(1) “Bus” means every motor vehicle designed for carrying more than ten (10) passengers and used for the transportation of persons and every motor vehicle, other than a taxicab, designed and used for the transportation of persons for compensation;
(5) “Motor home” means a motor vehicle designed to provide temporary living quarters, built onto an integral part of, or permanently attached to, a self-propelled motor vehicle chassis. The vehicle must contain permanently installed independent life-support systems;
(7) “School bus” means every motor vehicle owned by a public or governmental agency and operated for the transportation of children to or from school or privately owned and operated for compensation for the transportation of children to or from school;
27-14-213. Specially constructed and reconstructed vehicles.
(b) “Reconstructed vehicle” means every vehicle of a type required to be registered under this chapter materially altered from its original construction by the removal, addition, or substitution of essential parts, new or used.
27-14-214. Essential parts.
“Essential parts” means all integral and body parts of a vehicle of a type required to be registered under this chapter, the removal, alteration, or substitution of which would tend to conceal the identity of the vehicle or substantially alter its appearance, model, type, or mode of operation.
Subchapter 7 — Registration and Certificates of Title
27-14-707. Application for specially constructed, reconstructed, or foreign vehicles.
(a) (1) In the event the vehicle to be registered is a specially constructed, reconstructed, or foreign vehicle, that fact shall be stated in the application.
Sounds like a skoolie isn't a "school bus" anymore once it isn't owned and used by someone transporting children, it's not a "bus" if it's not operated for compensation, but it isn't a "motor home' until it has "permanently installed independent life-support systems." I guess it would be a truck while it's in limbo.
The law makes it sound sound like you can go to a Dept. of Finance & Administration office and get a "motor home" title once it's converted, if you note that it is a "reconstructed vehicle" on the title application, since the type and mode of operation have changed. It might or might not be just that easy. You would have to confirm ahead of time whether "reconstructed vehicle" is designed to describe a vehicle converted to a new purpose, or a salvage wreck rebuilt with replacement body parts. The law gives the agency lots of authority to create rules to fulfill its mission.
I don't know if the DFA would charge you $30 as a Class 3 pleasure vehicle over 4501 pounds, or $39-$1350 as a Class 2-7 truck based on gross weight.
I strongly suggest going to a rural office instead of a big city, whenever possible. They always seem to be able to spend more time with each customer, and seem to have the ability to separate non-standard legitimate requests from B.S. Big city clerks probably have heard too much B.S. They look at the line behind you, and the manager behind them, and say "No. Next."
(p.s. My after-school job for two years in high school was to drive to the DMV in the city every day, and stand in line in place of the customers of the local insurance agency. I quickly learned which clerks to line up for, and which to avoid.)