i have pondered this one for a decade. no doubt it can be done, trouble is, assuming a class c pusher, you'd want a good 300 hp, 3 phase motor at approx 1500 lbs deadweight. (http://www.baldor.com/products/specs.asp?1=1&page=1&catalogonly=1&catalo...). with 300 hp a standard bus/truck trans/axle would be practical. i know torque can be an issue but i think a 300 hp with nominal gearbox could move a bus up a grade at highway speed.

a skid pack diesel generator with sufficent kwh to turn the motor at the +-1800 rpm needed weighs in at 8100 lbs (http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_20031...)but the motor and skid pack makes for a complete system.

the gen would still have the juice to run the rv hvac and systems.

i think the rule of thumb says you might get double the mileage with hybrid diesel. assuming the generator used 3 gals in an hour, 60 mph = 20 mpg? (i haven't dug deep enough to get gallons per hour at load so that's just an ether example.) if it used 6, you'd be at current rv mpg's.

i'm quite sure the generator/motor combo outweighs a diesel plant by, at least, 3 tons so there's gvw to consider too.
anyway, i'm glad someone else is thinking about it. fyi, once i win the powerball, i'm building one. i'll keep you posted!

-jeff