Well, gee... if this subject should be open to first principles, and shouldn't necessarily fit an established thought process, methodology, philosophy or political agenda...
Which, to be fair: any of those things will save you a lot of time figuring out what the thing is, and gives you a base of people, ideas, material and budgets to work from. You just have to not mind that it's for some agenda.
...If we go back to the definition of "sustainable", then life itself is not sustainable. Life exists as an expression of the universe's increase of entropy over time.
Shall we then exterminate life, so as to maintain the world in a heightened state of potential energy?
Shall we give up entirely, as the universe is projected to end in heat death?
Shall we modify the rule -- include a moral imperative so that we should not exterminate life, but improve it instead?
"Sustainable life", then, to such extent as it can make sense (given the above!), implies a minimum (but nonzero!) quantity of life, with a high quality of life.
Might that be a reasonable goal to work towards? (As existing schemes go, there are several in this vein: the Voluntary Human Extinction Movement perhaps. Or more actively, the kind of work the Bill and Melinda Gates Foundation is doing: improved healthcare resulting in reduced childbirth rates, potentially below replacement levels.)
Perhaps we should sustain something else, like the product itself; how can a product survive a thousand years, let's say? Can it be self-regenerating? (Ah, but now we're asking to create life the hard way, which is even more counterproductive...)
All this is just to reflect on -- and perhaps become paralyzed by -- the definition of the concept, not even to attempt it.
As for implementation: whatever the concept is, one should then take actions which effect change towards that conceptual goal. This is similarly ill-defined, as one could run a program devoid of hardware at all -- a sufficiently well funded, long term, ad campaign could well do the job better than any hardware product could!
If instead, we are thinking on the smallest terms, of a simple product, the best we can do is to simply make the product, in the nearly cheapest way possible. Low price means strong sales means more uptake of the product, and, presumably, more completion of the overall goal. Low price means conventional production methods. Attempting to invent an alternative production method from scratch, is a non-starter: the result will be more expensive, and fewer end users will adopt the product!
But that said, you could attack the means of production: get into the business of production machines, and figure out ways to improve their sustainability. Now you have a knock-on benefit that multiplies your customers by their production figures! Again, cost of adoption is a problem, so you should be working also towards ways to reducing that cost.
Which really just sounds like business as usual, but with extra steps.
...
This isn't really to say anything useful. I could reflect upon what sustainability means to me, in the now, and what kinds of materials, products and methods should be used or developed to move things in that direction.
But as long as philosophy is on the table, I really just wanted to lay that nugget: that doing things the way they are usually done, is probably the best.
If the product itself is produced on a cleaner process, but is more expensive and therefore produced less, it's not really solving anything, is it?
The process might be messy, but the product can be clean, or helping to be cleaner anyway.
That's the general direction of things anyway. We didn't invent induction furnaces when we discovered iron. We invented the bloomery and the cupola first, and necessarily so. These are dirty methods, but they led to a clean production method, later.
I guess another good question is this: how much dirt can we withstand, in order to reach the next node in technology?
To put this in modern context, how much CO2 can we burn, without permanently screwing up the climate, before "renewable" (or whatever the alternative turns out to be) takes over?
How many lives do we need to support, before true sustainability will take over?
Tim