Hello Josh, and Welcome
Sounds like a bus conversion would fit your lifestyle very well. I'm working under similar goals / desires.
I am also very interested in external roll-down shutters. I had these with my apartment when I lived in Germany and loved them!
As far as I know, clear water is fresh water, ready to be used.
Grey water is waste water from showering or the sink drain.
Fifer and I worked out a plan for our roof-top garden, where we use pots with built-in water reservoirs (grow-box / earth-box type...) When we park, we'll place the boxes on the roof and fill them with water. When we're ready to drive, we'll drain most of the water and lower then down into the body. That was we don't have to worry about the weight or the wind. Also, we're assuming that using pots helps to reduce the amount of soil (weight) you need for the same number of plants.
As for your pop-top bedroom. I've seen several buses where people take old VW Camper buses (with pop-tops) and mount them on their roofs. I'm not sure of the implications, but it's instant pop-top.