Let me add an observation, Pieter. You wrote “CPE Bach … Usable in every key”.
Let me check with Eulenburg’s English Edition of CPE’s Versuch, p. 37: “All twenty-four tonalities will thus become usable”. So far so good.
But then you write that CPE tuning will be “Not necessarily almost equal”.
Actually, a few lines later CPE clarified: "The keyboard plays equally in tune in all twenty-four tonalities”. And even if he had not, if you follow his advice to “take away from most of the fifths a barely noticeable amount of their absolute purity”, an almost-equal temperament is the consequence, and this can be (and has been) mathematically proved.
Actually, since I don’t play solely French music for a program very often, I would say that the most common tuning temperament I use is the Bach/Lehman tuning. In addition, speed and accuracy come from the quantity of harpsichords I’ve tuned over the years, often for high level concerts, so I had to do a superb job in a limited amount of time. I was not fast when I was new, or only tuning for myself (only the first year!).