If you are looking for a small RV I might suggest that you look at one on a
Chevy Chassis they will get a bit better mileage than ones on a Ford Chassis and offer more comfort and better ride.
My 26Q Tioga on a Chevy chassis gets between 9.2 and 9.7 MPG depending on speed and wind.
I would also try to get one with a walk around bed and not one of the ones with the corner bed.There a many out there that have a full bed in a slide out.
I think that the ones that caution about buying a small RV have done so to put the family in and find that the tight quarters of a RV is not meant for a lot of people.Whereas with just a couple it may very well work out just right.
What you have to do is look at the floor plan that you might like then go look and walk around and see how it will fit your needs and comfort level,looking at the floor plan of your trailer I think you would find something just as nice and functional in a small RV.
Good Luck in your quest in finding the one that will fill all your needs and comfort level.