What would be possible – is to hack the communication interface between the UI front panel and the main board. This should be doable. Just breakout the connection cable and work out the signals with a logic analyzer, while strategically causing the two boards to communicate. Once you had the communication worked out you could substitute your own “main board” for audio generation with your own communication software to run the interface.
Now what this would give you, is of marginal value, but worth consideration. The mechanical interface on let’s say a Digitone or Digitakt, is quite nice and could be repurposed quite reasonably. The metal box is generous and substantial and could accommodate a variety of substitute “main boards” of you own creation, lots of choices for that. Heck an arduino by itself would be sufficient for your own midi controller/sequencer if you wanted that alone.
If you happened to have an Elektron box with a good UI board, that you could acquire inexpensively, because the mainboard was busted, it would be a fun project. It certainly would draw a look, if you had something like a granular synth running on your own “mainboard” in a Digitakt? Or what have you.
You’ll need a fair amount of background to do all this, and it would take some time, but it is doable. I’ve looked into it enough to see that it’s something i could do.