pappawheely
Autonomous4X4
One obvious downside is that it'll cost several times more for the unit than something like the Thetford Curve. A less obvious issue is that I'm worried you'll have to work to get one . . . Dometic handles Thetford in North America and, just as they did with the Seitz acrylic windows they distribute, it seems they've decided that to sell only to builders. Annoying, since these are over the counter items in Europe. You may have to order from abroad, buy used off eBay, or cajole a builder into getting one for you. Still, it might be worth the effort and cost. If nothing else, you'll probably only be emptying it half as often.
Thetford will not sell retail, I tried. I ended up buying from England through ebay. Even with shipping and customs I saved about $300 from the retail quotes I got from RV dealers. 100% of the so-called dealers did not know what a cassette toilet was.