I have tought about a side isle myself. It would allow larger un-broken rooms and other sections.
And I like the idea of the raised floor. One more step into the bus would not likely be a noticable nuisance.
This would create a fabulous space to put water tanks and such.
You could probably get away with shaving a couple of inches off the top of the wheel wells -- unless you might ever need to use snow chains.
You would be raising the floor less that one foot. I lifted my roof two feet. Piece of cake!