I've done this before and it's significantly more than trivial.
Sure with "added extra circuitry" we could do lots of things but are there enough pins available for these functions? S-Meters would require a voltage reading on an analog pin - is one available? Looks to me like there _may_ be at least one. There are definately some spare digital pins (CW keyer anyone?) which could be used to replace the pot for a rotary encoder in tune freeing up more analog pins.
More input buttons (to select options etc?) could be added onto an analog input using a set of resistors. I dunno what that's called but you feed a series of switches with various resistor values from a 5V source and then measure the voltage. different voltages equate to different button presses.
All of these things would require chopping up the board to rewire some of the Nano's pins.
Perhaps some sort of computer control could be enacted over the USB serial port. Make the Radiuno speak Elecraft? Or perhaps computer CW keying for contests etc?
And then there's the code room. Other libraries may consume more room than we would like. Code certainly will.
