I've managed to compile a working firmware with this config: https://github.com/gleber/qmk_firmware/commit/54078ec73c0ff2bd01984242f748a837c1954d03
This isn't tested much, just the basics: keys and split setup. LED, bootloader magic key and any other features are not yet implemented. Tested only the Miryoku layout so far.
I've disassembled it and found a few things.