If you can wait I would hold off for a couple of years and wait for the Ford Transit based motorhomes. With the Ford Eco-Boost Turbo 3.5L V-6 it will have the power of the V-10 with better gas mileage than the V-8. Analysis of the stripped cab version wheelbase indicates up to a 27-foot length could be supported.
There has been some interesting commentary about lack of availability of V-10s from Ford causing Triple-E Class B+ models to be dropped. Myself I think the lack of availability is Ford reducing the supply to move manufacturers toward the Transit, so I think its debut is not far off.
These already exist of course overseas:
