I’m curious how a factory reman trans would solve the dilemma.
You are correct that a typical 150,000+ Mile MINI is not likely worth a 7~9000 trans.
But if a local rebuild is 4500, then a factory reman would likely cost 6000. In no case would it be less than the local rebuilder. So I really doesn’t solve the issue except for the likely better warranty.
i have an R56 with the Aisin and 172000 miles a fervent hope that the trans doesn’t die, because there’s no way the car can merit a six-grand repair. It will get a junkyard takeout. You really have to consider that this same dilemma applies to *most* cars out there, especially the lower price-class cars like our MINIs. It’s just a fact of economics.

what you’re describing (unfortunately) is not a MINI phenomenon; modern auto trans units are stupid-expensive to overhaul and dramatically more involved than the old school 3-speed Turbo 350 (GM) or the Torqueflite from Chrysler. Modern units have five to 9(!) speeds and a pile of electronics, many of which have to be replaced at rebuild. A Mustang or Tahoe or F150 trans job is also thousands of dollars these days. The point I’m getting at is that the economics suck for most modern cars once they age. Damned few cars out there at this kind of mileage can justify a 4-5000 dollar repair. Potential availability of a factory reman unit would in no way help that math because it won’t be cheaper than 4500. We have old “modern” cars that aren’t worth enough to justify the cost to repair their modern components. Price a reman engine(!) I know someone whose Edge needs a sunroof repair that costs $3500! The idea that the mfr might have a ‘duty’ to supply lower cost parts to keep their older cars on the road longer....is silly. They’re in business to sell new cars, not prop up old ones (which prevents a customer from buying another new one).
No, the point is that we just have accept the fact that buying used parts us a thing. It’s a very sensible thing at that.