With that kind of variability of taste the poor manufacturers stand little chance of ever getting compatibility, far less a standard..
Tail wagging the dog.
A manufacturer that allows the customer to determine the design of equipment is on a loser from the off. They'll get no sympathy from me, and if they carry on producing products that way, they'll remain poor. Feedback is useful, suggestions welcome, ideas accepted, but the design should not follow any but considered and digested processes: function, flexibility, economy. The one-fewer-frame story you tell shows that both parties were expert ditherers, and that the average beekeeper has no interest in the broad benefits of uniform design or the economical use of ergonomics, material or production. Few are able to work up a good idea and if they do, it can be knocked up cheaply in wood; too many of the beginners we see don't even know how to hold a hammer, bless 'em.
At the supply end, you'd think that a manufacturer would go out of its way to adopt a deep and abiding interest in the benefits of uniform and economical use of ergonomics, material and production. Maybe beekeepers aren't best equipped to design equipment? Perhaps handing the job to computer designers is unwise? What persuaded Maisemore to produce a polynuc without beespace between topbars and roof? Why did Swienty make that awful roof? Why did Paynes waste poly and money on extending the porch on their poly floor? Paynes could have saved both had they read page 60 of Manley's
Honey Farming, where 54 years ago he dealt bluntly with floor projections. Either they want to lock the customer into their unique system (thereby shutting themselves out of mix'n'match sales to users of significant UK National stock) or they really don't know what they're doing (not out of the question) or they don't trial them for long enough to reveal the drawbacks (that much is obvious), or they think the customer is not skilled enough to notice (often true).
Once the £10k has been spent on a mould it's too late, and when they wake up to the problem, all they can do is offer a workaround or hope to sell enough of a compromised product to enable them to recoup the £10k. That could be many years, given the flock of designs descending on the small field of National corn. As I said, no sympathy from me: if manufacturers let customers determine the product we could end up with a kettle with two spouts or a car with a square steering wheel (been done, in Britain, of course).
Agreed: 2-frame mating nucs are the ultimate: minimal expense and maximum return, and the same lean recipe ought to apply whether coming out of winter with a 10% loss for a 10-hive owner (who may only want to make up the loss, cope with swarming and re-queen a few more) to a 10% loss of 1000 stocks with nuc orders to fill. Still, I reckon that as the third frame would be foundation or comb, the economy of two live frames is maintained, a breathing space is gained, and the beekeeper's bacon is saved. My initial experience of overwintering late queens in these BS 3-frame twinstocks is good, and though autumn wasps might seem to predicate against success, the 3-frames were strong by then, and they ought to be ready for upgrading early this season. That's functional flexibility at a reasonable cost (if bought by the pallet).