...Thorn's expertise with hub gears fits well with the high end mid drive motors. It's a fast moving technology, that maybe doesn't favour those producing for longevity at the cost that involves, but I simply don't believe it can be ignored.
Couple of really important points there. Hub gears are a given base expectation on an upmarket electric bike. However, my experience, and the expectation of most electric bike owners who have thought about the matter, is that an electric motor for a bike is not a capital asset but a consumable expense, just like its battery; the electronics controlling both may or may not last well: my experience is not. Paradoxically, the batteries for my electric bikes give every appearance of responding well to a rigorous schedule of recharging to keep them fully charged after even minor current draws, and have already outlasted one motor and control system but I doubt that in the long run this will be a general experience: the other electric bike owners I meet have no bicycling background, and without exception they abuse the batteries, and that leads to general dissatisfaction with their electric bikes; a common trope is, "Can I buy your [clearly succesful] electric bike instead?"
I think Thorn, and other small quality bike makers, are between the devil and the deep blue sea here: a maker of quality bikes, at least some of whose customers may aspire to leave their bike to their grandchildren, could easily harm its reputation if they fit even the best of the current crop of Chinese motors (Bafang is the most advanced and popular) with their known MTBF (mean time between failures) being obviously so much lower than the practically infinite useful lifespan of a Rohloff hub gearbox or a Thorn frame.
It's just one of those problems that it helps to be a large manufacturer to solve, because reputational damage to one of many lines will not be as financially damaging as loss of faith in a single or one of a few product lines.
Utopia, often said to make the best bikes in the world (and they do make a really good bike -- I have one and it is eminently satisfactory, but you pay something in the order of double the Thorn price for it, and up from there), when they first made an electric bike because their clientele demanded it, solved the quality problem by fitting well-proven heavy industrial type motors from The Netherlands to the front wheels, and providing a facility (double-sided "pannier" batteries hanging over the rack, with soft touring panniers fitting over the battery "panniers") for doubling the battery power then thought adequate for a utility or commuter bike to give some approach to a touring range on at least the routes with charging stations that were then already in existence in Austria and part of Germany, and projected to be widespread quite soon. They also had their own control electronics developed, in their usual cost-no-object style. The whole affair was stylish, mechanically simple, hefty, unbreakable, and
heavy. I totted up the weights and did my own electrification for about a quarter of the initial price of Utopia reliability, but got a lighter, much nimbler bike, together with the knowledge that in the end I would probably spend Utopia money on replacements of various electrical and electronic components every few years, which is how it worked out. But imagine if I was some solid German burgher who Utopia sold a bike with my sort of lightweight consumable electric motor and associated components -- I wouldn't count on the fellow being reasonable or quiet about his disappointment when inevitably it wore out in three years or so.
In this regard the only important differences between Utopia and Thorn are:
1. The typical Thorn customer is a knowledgeable long-time cyclist who does his own maintenance. The Utopia customer spends money instead of experience and anyway takes his bike to be serviced once a year by the dealer (his ten-year guarantee, which is very valuable, depends on it).
2. Thorn is saddled* with an "exceptional value for money" image; that is exactly what right now an electric bike is not, value for money. (Oh, sure, I, and several others here with very specific and thoroughly costed but actually rather particular personal problems to do with our health to solve, consider our electric bike installations good value for keeping us cycling, for the fresh air and the exercise, which is of very high value to us, but ours are not universal calculations of value.) Eventually, since an electric motor and its control electronics are a well-understood standard set of components, the only conflicting bicycle requirement being low mass, which is not an insuperable problem, and presumably quite soon, electric bike components will become more reliable without the price increasing too much, and then, as has been said in this thread already, Thorn won't be able to stay out.
* Peculiar times we live in when a good reputation for providing a quality article at a value-for-money price can be described as even marginally a drag on innovation.
