>> It would be great to implement the K3 protocol, so I could use the front panel. I could use Digital potentiometers for the pots on the board.
Using the K3 digital pots means the uBitx would have to have the mechanical pots replaced with digital driven ICs. That would
be limited to mic gain and rx audio gain. Doable but not trivial. Same for other features that require hardware not implemented
in the ubitx. However if the Radiono controls it you can implement a protocol to do it from whatever hardware you want to use.
>> I could even mount the uBitx inside the K3/0.<<
Space permitting, you may need more power too.
You may look at Andy's, KB1OIQ work for ideas not mentioned here.