Well Thorpedo if you're such a smarty pants ridiculing others choices, how come you need help?
Not exactly rockets science with 12 volt electrics!
Before you jump in, you'll be adding another micro switch, pump and valve probably. That adds to the amount of things that break down due to occasional use and seizing up or corrosion or just usage. Also when you come to sell the van you have non standard set-up unless you can remove it leaving no trace.
Unless you are always on a fully serviced pitch the toilet will exhaust the water supply that your or family have to haul, only a little quicker I know. It's your choice and time, you still have to add chemical so I for one can't see what the trouble is in splashing a little H2o at the same time. We caravanned for six months last year I doubt that I filled the toilet tank more than 15 times in 26 weeks in the van, I doubt that it took as much time as you've spent typing in this thread. With to many years of caravanning experience to remember it just never occurred to me that adding water with chemical was such a chore that I might need it done automatically whist still needing to add the chemical manually.
Oh yes, our choice of 4 x 4 is comfortable and with 300+ HP and 700 + NM of torque 4 x 4 is the best option wherever you drive it, but ours does go off road if you really want to know.
As for the "grown up" cheap shot. A grown up would know that a Satnav does more than just navigate so its on all the time the car is running if you want to make good use of it, and its smarter than you Thorpedo. You can wake it up anywhere in Europe and with a flash at the sky it knows where it is in a flash unlike you or anyone else! It always knows where the nearest pub, hospital, restaurant, supermarket, fuel station or many other useful places you may need to use or find whilst driving or caravanning.
Happy vanning and happy DIYing, enjoy