design philosophy is an interesting term. For me it meant near zero setup time, space, long term independent travel in remote Aus and beyond, internal living, ergonomic, self-sufficient and sustainable, well ventilated, easy to live in, easily built, reliable, fault tolerant, self-diagnosing, lightweight, vast storage, etc. It all just rolls off the tongue.
Its difficult to describe in a spec what it means to have four people standing inside without feeling uncomfortably close to each other. And to have 6 people seated for long periods without squirming (technical equivalent of "beam me up scottie"). Then moving and sleeping for two. On an inner-sprung mattress. Specs will have "seating for 6", but not for how long. A comfortable bed in the spec, but not how comfortable - my hips ache, buts of course its my hips not the bed!
Zero setup time is not just about having the first cup of coffee within 5 minutes of stopping, for me its about the shower and loo that are "always there", minimal multi-use space, but I have a one minute changeover from seating to bedding.
Ergonomics is important to me. A small thing but I mistakenly reversed the lever taps (faucets?) on return to Aus. Simply not as convenient. A cooker that is a little too far back in the bench so lifting heavy pans is a strain on the crook back. Space to me is a 2m x 600mm contiguous bench top among other things. My wife likes to clutter it up, which means its easier to put things on the bench than where they belong, which may mean a design flaw somewhere (though I doubt I can redesign my wife). It got worse when the ball bearings fell out of some of the drawer runners. Though of course the clean lines and elegant design meant that finding the ball bearings was cinchy.
Ergonomic gets me to doors among many things. It will be close to an engineering miracle when a full size door appears with a pop-top, either solid or floppy. I've seen it on a 16 tonne 6x6 solid lift up 2-storey. When the hydraulics burst access was impossible. I resorted to a post tensioned solid side drop top design. Marketing can work wonders and turn a head banging short door into an accessible feature. Commercial and other promotional imperatives may obfuscate.
If I was in marketing I would describe my design as having evolved from the tensioned arch design of the Sydney Opera House to achieve unparalleled strength with rigidity and flexibility. The shell is an advanced frameless design meticulously built to engineering tolerances to ensure perfectly fitting parts joined with high tech adhesives. But I'm not, so it has a couple of rigging wires with turnbuckles to hold the roof on to a box that's glued together..
There's probably more time spent on designing steps for access than any other part. Consistent step heights is more important to me than absolute pitch and angle - my last step is 20mm height difference to the others, and 25mm less deep, I've lost count of the number of times I've said to visitors "be careful on the top step". But I doubt that will ever show up on anyone's spec sheet.
Light switches were brilliantly placed next to my custom made led light fittings. Great until I could no longer lift my arms above shoulder height (a minor medical hiccough). "Can you turn the light on please" is about as frustrating as life can become for both. I solved the shadows on the bench problem with a "W" of led strips, others solve it differently. Oops, I forgot - lighting is carefully designed to flexibly provide both general and task lighting in an infinite variety of formats.
Specs are easy and objective. But engineering is only part of the story. Design can be an elusive, subjective, pragmatic balance of form and function. A series of compromises. The specs may read the same, but the outcome can be radically different.
Mostly finding the right tool for the job is an iterative process starting from the clean sheet of paper and the uncluttered mind. Constrained by "what do I want to achieve" and "what's available". Potentially constrained by "marketing" and "dominant design" despite our best efforts to escape. Certainly constrained by engineering feasibility, though it will be nice when someone develops a sky hook to go with the perpetual motion.
Neither the chicken nor the egg came first. It was an iterative evolution. So is finding the balance between "what I want" and "what is available".
Always remember that one person's pride and joy is another's ugly baby. And I doubt that any of us are truly objective and realistic about our own designs.
All that on what is basically a Japanese delivery truck which in the cold hard light of objective thought has limitations which may be considered by some to render it just a tad unfit for a different purpose. But what alternatives are there within the constraints. So we get engineering to modify them. And marketing to turn a deficiency into a feature.
Perhaps a little disingenuous though to label it a "global vehicle" when head office don't provide local agents with direct access to the parts book. "Have you got one of these?" seemed to be so much more successful than "I need a radiator cap for an Australian spec 2005 FG649E". And "this is the part number for the wheel studs" seemed to remove the blockage caused by lack of parts availability.
All the above posts are saying the same thing in different ways - there's more to life than specs and aquiring the vehicle that fits the need is a journey. Your greatest asset will be the critical thinking useful in wading through the quagmire.