Hi Folks, Looks like a great choice for a camper.
These shorty's are super maneuverable, mine will do a u turn on most secondary roads, waaay tighter than my pickup. Does take a while to get used to the width and driving with that glass entry door is pretty distracting at first!
My primary area of travel is in British Columbia so my build reflects that. In you're climate you will have different needs.
I have some similarities in layout.
My kitchen and table layout is about the same as yours but I do not have a loo behind the drivers seat. I have good rear visibility through the side windows and the back door. I have a small open space behind the drivers seat which will accommodate a fridge (the top would add to counter space) right now a cooler lives there. I installed a propane heater under the table, also a bit of storage space under it. Same front passenger captains chair with built in shoulder harness but mounted closer to the center so your feet don't hang over the stairs. Seat moves forward and back about a foot as well as rotates 360. Rather than add a drop leaf I sculpted the table to allow the chair to rotate. I left a bus seat in place over the wheel well for the rear table seat.
I like having good access to the rear door so built a fold up double bed on the rear passenger side. It uses up 7' in length and allows some storage on the back end. When the bed is folded up there is good access to the under bed storage (also good vision out rear door). On the back drivers side there is a small fridge over the wheel well, then a closet then a storage bench with a litter box in it. I can't convince myself to install a bathroom in a small bus. I might add a hot water system, then for sure I would rig up an outside shower hose.
I'm happy with my bed design but may change the whole rear lay out anyway. Sometimes my wife doesn't want to come camping and suddenly I don't need a double bed but rather 2 singles.
My thoughts on your bus-
Once the mechanical stuff was deemed in order I would get some white paint on that roof, maybe the whole bus!
It really helps and will extend the time you can work inside it.
I would consider an awning and 1 or 2 pull out drawers on the outside of the bus to facilitate an outdoor kitchen. The awning might be a plus while doing the build.
You are going to be making thousands of trips in and out of the bus while building and all the big items want to go through the back door. Setting up a ramp to about the height of the bottom of your rear bumper is time well rewarded.
I now have a rear carrying rack/step that plugs in to my hitch receiver, wish i'da figured that out first thing.