I have started modifications of both the assigner CPU firmware code and the voice board CPU firmware to try to add some or all of the features below. So far unison detune has been proved working. In my current software I have temporarily disabled portamento control and instead use the portamento pot to control detune spread amount. The patch to replace portamento with unison detune is just 43 bytes, amazing what you can acheive with full hardware control...
The Junior 106, hood opened for easy EPROM access
Here's a sound sample of the Juno 106 with this mod, read my SoundCloud comments to see what I change at various points.
DOWNLOAD THE WAV file to get a more realistic experience, the mpeg artifacts are quite noticable in the mp3 version you get in the web browser.
Features that I currently investigate if they are possible to add. A problem is that the assigner (main) CPU firmware is quite full (8k code) so I will probably have to sacrifice some features of the original Juno 106 to fit some of these mods. Tape backup / read comes to mind.
Add velocity sensitivity via MIDI. Should be doable since the MKS-7 has it, and it is basically a Juno-106+TR707 inside.
Create some kind of multitimbrality. Doable due to the same reason as 1. All oscillators share the same PWM, waveform selects, resonance and final VCA though so the only parameters that are open for multitimbrality are LFO and Envelope controls for pitch, filter cutoff and voice VCA.
Random patch generator
Extended MIDI control receive/transmit. For example let the pitch bender transmit a on a selectable MIDI Ctrl number, And let the VCF freq, or other parameters, listen to a selectable incoming MIDI controller number.
Let the pitch bender control other parameters than just VCF freq or VCO freq
Add new waveforms to the LFO. Might need alterations in the module board CPU code as well though.