I haven’t built a musical keyboard, but I’ve taken apart a home (electric) organ or two. I hear that one among the many options you have if a modern pipe organ is being made for you, is different strengths of magnets that initially impede your keypresses, like the pneumatic valves would if it weren’t electronically controlled; as well as different woods for your keys. There’s a channel on YouTube to which I’m subscribed where the guy is building his own tiny pipe organ (like, 30 pipes, the size of a large suitcase).
The hexagonal key layout mentioned by others, and also often seen on one side of an accordion, is one among several alternative musical keyboard layouts: the white and black keys are sort of a musical QWERTY. Not the best, but the largest installed base, the most likely for new people to learn, and the most likely to be attached to an arbitrary keyboard instrument you come upon.
My ergo journey started with similar requirements to yours - specifically including the Y and B keys. Along the way, I learned how important layers are for comfort, ditched QWERTY entirely for Colemak DH, bought a 3D printer, and ended up at 40%. Several years ago, there was a term “1KFH” (“one key from home”) people used to describe the amazing amount of comfort they found when they never had to move their fingers more than one key away from home position, nor to move their hands.
I’m not saying you have to change your requirements, now or ever, but I think people who start to make their own ergo keyboards may be subject to this sort of requirements drift, such that if they ever make it to the product phase, their products aren’t what they initially expected to be building. And maybe this sort of dynamic is what makes it less likely for the product you are looking for to have been built already.