unfortunately hybrid motorhomes won't save much fuel. the average rv has approximately 90 square feet of frontal area and a coefficient of drag of about .45. if you work out all of the math involved (like i just did) you find that this rv will require a continuous 118 horsepower at 60mph, and 172 horsepower at 70 mph. a hybrid drive system won't help you with continuous loads like this.
if you were to make a motorhome front wheel drive and get rid of the hypoid gear in the differential you could save approximately 10% of your fuel burn.
if you worked on the vehicles aerodynamics and lowered the coefficient of drag to .30, you would only need 91 horsepower at 60 mph, or 129 horsepower at 70 mph.
as far as the recycling shower goes, it's a great idea for a motor home. these are currently manufactured right now for high end home use (think 10 or twelve massaging shower heads). they pump water out of the shower basin, filter it, re-heat it, and spray it right back out. this ends up being alot cleaner than sitting in a bathtub full of soapy water.