I like the idea of storage to the very rear. I would then have a bedroom forward from there and closet, then a shower on one side and toilet closet across the hall. Then a galley on one side and on the other the fridge and a washer/dryer (stacked and bolted or one unit that does both). Then forward the salon seating with a dinete to one side, taking the seating up to the front and have a passenger seat up front facing forward.
You might take a look a yachts for sale on various sites and see how they are laid out to balance the load. What you put on one side in weight should be countered with about the same weight and don't forget tankage under the floor that will have weight offset. Fresh water tank I'd think should go back as far as you can get it near the rear axel, with the above, you black water tank would be just forward of the rear axel. Gray can go on the other side.
I'd also suggest you not use RV fixtures and appliances, use a home hotwater heater, vented furnance, use a home A/C window unit and build a drain pan and hose to get water and condensation out, don't hang it out a window.
A small pressure tank will keepwater pressure up to home grade faucets at sinks and shower. You'll want a good generator in your garage area, vented and makes sure that rear bedroom wall is tight and sealed if you run that inside, box it in back there with a vented exterior access.
Can't wait to see the rack you build on top with a ladder near the side door and an awning off the door side. You'll have a great platform up there for a clean patio area and lawn chairs to watch the fireworks or the stars.
If I were taking by bike, I wouldn't use 8' in the back, but I'd have a shorter garage/storage area, I'd have a bike rack on the back that raised up and secured to the back door level, a lift can do that and would make it easy to load and unload.
I've always wanted to get a Blue Bird bus and do this, but gotta be honest, I don't want one that looks like a school bus conversion because so many are so poorly done that there is some shunning going on at campgrounds and private property. I'd consider an exterior skin and changing the windows to get that motorhome look, that would be first class. But, leave it and leave it yellow if ya like if you're going to boondock on your own anway...who cares!
I'd say don't use a 2x4 when a 2x2 or a 1x2 will do the same thing. Many build a house inside with 2x4s, it's just stealing weight capacity and running up the expense. For example to fur out the walls, use furring strips, 1x2s or 2x2s instead of 2x4s, all these do is keep the wall covering from falling off the side and you don't need 30" stud walls for that. The space for insulation is sufficient at 2" imo, look at the efficiency of the windows....why have 6" of wall insulation.
I'd use pex tubbing for all water lines, it is less likely to burst if frozen and pvc drains. Hot water lines short and insulated off the exterior wall. Electrical to code on 120v, you may only use a clothes washer/dryer with shore power, but I'd sure have it if I had all that space. If you lay it out right, you could have a small fireplace!
Not only do you need to look at a floor plan, but think virtically as well, maybe a access door in the storage area but your inverter may be under the bed or boxed off on the floor of the closet with a shoe rack above it. Take advanatage of under seat storage. Make sure electrical gizzmos have ventilation with cirulating air. As mentioned, magnetic catches on cabinets may work, but if you're going to twist that frame much getting to the river, check out marine latches or lock'em down. I would not use base cabinets in a bus, they are too deep unless you cut them down in the back. Use smaller upper cabinets IMO.
Look again at boat building sites, wooden boat, many of the attachment techniques used in boats are best for RVs too, glue and screw, go light!
I was really bored, thanks!
queen bed matress in back above a "basement" for storage...his and her closets curb and drivers side..then cassette toilet and shower across..counter on curb side ..long sofa across....