Jack, I don't categorically disagree with you, but perhaps The Well-Tempered Clavier might have been written for an equal-tempered keyboard, as that tuning was certainly being discussed as a "good" tuning by the 1720s when the piece was written, and Bach was certainly aware of it. Meantone would not have worked at all for that particular opus.

As an aside, Paul Groff (now in Florida) has researched the original tunings of Jeffries anglo concertinas, and has confirmed that a number of the accidentals were tuned differently as enharmonics, (i.e. a C# was tuned differently from a Db, etc.), though I don't know which chords were used to determine exactly how this was done. But he now will tune your instrument this way, if that's what you want!

Capt. Birdseye on an English concertina will stay with equal temperament I'm sure.