Also, if you're parking in one spot for awhile, I'd consider a bladder to put on roof. (How strong is your roof?)
That way it would absorb a bit of energy so you'd have warm water. It would also shield the camper from direct sun. It would keep the place just a bit cooler.
Gravity would be your friend too. No pumping for showers, toilet, sink etc. just once, to get water up top. You could use a little 12v bilge pump for that.
I'll be starting my own project soon. I may use some of the ideas that come up in this thread.
The seller of this (soon to be GXV) will be dropping it off in a week.
There is a power tailgate coming with it too.
It's really slow, but it ain't for racing.