For electronic musical instruments, which in theory ought to only be limited by our imagination, it seems rather arbitrary and limiting to have synthesizers that can only be played like a piano. Users that just want an electronic piano are well served by the status quo, but "all music" is a broader category than "all music that is intelligibly playable using a piano-like interface in 12-tone equal temperament."
The ubiquity of MIDI and its piano-centric design has meant that it's been a very uphill battle trying to do any kind of electronic music that isn't plain 12-edo piano music. That's a shame. We've lost out on a lot of interesting music that could have happened if it was just a little easier.
MPE at least has made it reasonably possible for things like the Linnstrument to exist and be commercially successful.
I know it is different from what you want but Korg gives you the possibility to use other tunings on the Mono/Minilogue (XD) models. Aphex Twin made several availlable for download.
Yeah, lots of synthesizers have that feature, but the problem is that it's accomplished "client side", by the synth. It recieves a MIDI message that says "Play me a D" and the minilogue in Werckmeister mode plays a D detuned by 6 cents instead. Crucially, it makes the instrument play something different than what the controller asked for.
Unless your entire setup is composed only of Minilogues all configured in the same tuning settings, your electronic instruments will be out of tune with each other. Plug in an old yamaha because you like the sound? Now everything is out of tune. This isn't supposed to happen in a MIDI workflow.
It would be much better to be able to specify tuning system in the midi messages itself, so that any instrument, hardware, software, or whatever, knows to make it's Ds 6 cents flat so your whole electronic orchestra can be in Werckmeister tuning together, instead of just the one minilogue.
The ubiquity of MIDI and its piano-centric design has meant that it's been a very uphill battle trying to do any kind of electronic music that isn't plain 12-edo piano music. That's a shame. We've lost out on a lot of interesting music that could have happened if it was just a little easier.
MPE at least has made it reasonably possible for things like the Linnstrument to exist and be commercially successful.