I have a similar idea...
I opened my E-Mu XBoard25 keyboard and found out that there is a perfect place with definitely enough space to implant an Axoloti, namely above the battery compartment.
Therefore, it seems very attractive to me to make a real, stand-alone synthesizer of this device.
I'm not yet sure if I make the connection via MIDI or USB-MIDI, and how to unite the power supplies. And some more mechanical considerations are to be made, like a back plate design. But it should be relatively easy.
Maybe I can even retain all the original functionality as well.
I think we could collect and share here our findings about the suitability of all sorts of MIDI devices, couldn't we?
What I think would be very attractive for implanting is the Behringer BCR2000. Does anyone here have one and could check if there is space left inside?
"Axolotify your MIDI device!"