My problem is Brian that I could never farm out the build because I like to make every decision and in fact it's common to change the design based on something you just did. If you get someone else to build it then you have to get the design 100% right before you start, something I've never been able to do

I guess they will make adjustments as they go but at some point they will say enough is enough.
I should think that it could be very easy to get someone else to build this thing for you, and for not much more than your estimated build costs.
There is the Uro-camper guys. I love what they are doing and they have a Cruiser version prototype, maybe I should get a price from them.
The FG would seem like a possible option for you,
Yes I reckon a Canter/Fuso is possibly the sweet spot re the size, small enough to go most places and large enough to be comfortable. I could have gone either way I think, there just happened to be a good Cruiser for sale nearby and I'm impatient and lazy
I hate the fact that on a 4x4 you lose so much space to the bonnet, but OTOH if you put the bed over the cab (something it's hard to do with a Fuso) you get most of that back so there's not as much difference as one might first think.
Why did you not choose to go with glass?
In what way?
The panels I'd like to use are a fibreglass composite, they are definitely not "budget friendly" but they are self-coloured and include insulation so that helps. If you mean glass panels over a steel frame that would probably be cheap although if I build a frame I would probably be inclined to use materials I have experience with.
I love the idea of a monocoque body with composite panels, but I confess I'm a lot more comfortable with a steel frame. Very rough calcs indicate ali over steel would weight about twice composite panels. Glass panels would probably weigh about the same as thin ali.
The other option is a full glass monocoque body, that's so far out of my comfort zone I can't even see it.