I know little of the Bongo but love the name. "We motored to the coast in the Rover" sounds serious, "We went to the beach in the Bongo" sounds like a cheerful outing.
I had an aircoooled T2 VW back in the late 70's when you could buy second hand for next to nothing, panorama screen high indicator, early 1600 cc twin port for the enthusisats out there. It was a proper Devon conversion with pop top, and most of the furniture was softwood framed with fairly thin ply over: I don't recall the details. It was sturdy enough. I did a couple of mods, cupboard for the crampons and ice axes, and there is a tendency to 'over-build'. We like things to look and be sturdy, but weight is the enemy.
Somewhere (perhaps in the registration document or handbook, perhaps a plate rivetted on a door pillar) will be the unladen weight and the permittted maximum gross vehicle weight. The ULW may be fully fitted if its a factory conversion but may well be bare chassis/body without the rising roof. Somwhere between ULW and GVW youi need to allow for people, petrol, maybe extrat battery, stuff and things, leisure stuff if you take bikes etc, water maybe, and the furniture. Aside from the obvious advantage of keeping it light there is that technical constraint and often there is not much scope in that ULW/GVW gap. You might need to compromise your high standards of woodworking and focus more on the weight.
I also wonder (but you can't calculate for any of this) if "light and weak" is helpful in an accident. Imagine a tail end shunt, the vehicle does its proper progressive crumple, it might be better if the big horizontal sheet of timber in the back also breaks rather than gets pushed forward to damage the occupants or ends up flying about around the occupants.
You may know about tyres, there are the usual width/profile/diameter/speed rating numbers: 215/55 17 W. They are follwed by load ratings, typically 91 or similar. Higher number = higher load rating. If you go up you might get a slightly harsher ride - I've never noticed it - but no other downsides to my knowledge. Because camper vans are carrying most of their weight most of the time, if tyres ever need replacing make sure the load rating is the same or higher that what is on now.
There is a company called Bilbo, been around for aeons, who do conversions designed so you can take bits or modules out to use the van as a van: might be worth a look around their website for ideas.
, that I use for round the house projects so that is going to be the main tools I’ll use. I did snag a FTAGH router a while back so that is going to be a big help. The only thing I think I might be missing is a track saw. I don’t have a table saw and the 18V cordless is not the most accurate of tools. A finer blade might help. Just been checking out eBay to see what’s available on the track saw front. 
those are the vehicles in question, though the later models.
Camping in a Ford Escort sized van is.... um... ambitious....
