I think the Lumatone uses MIDI 2.0, but I haven't actually seen one of those in person.
I'm working on my own microtonal MIDI controller, and for now it makes more sense to just use MPE. Maybe I'll support MIDI 2.0 eventually, but I'm kind of waiting to see if MIDI 2.0 is a flop first.
MPE is very useful if you want real time per-note expression and pitch control. (Basically, the less like a piano your controller is, the more useful MPE becomes.)
It's possible to do that in plain MIDI 1.0 by using a separate channel for each note and using CCs, channel pressure, and/or pitch bend (that's basically what MPE does), but trying to get that to work with a wide range of synths is quite difficult because every synth implements MIDI a little differently. MPE standardizes that use case so it's much easier to have something that "just works".
I'm working on my own microtonal MIDI controller, and for now it makes more sense to just use MPE. Maybe I'll support MIDI 2.0 eventually, but I'm kind of waiting to see if MIDI 2.0 is a flop first.