In my opinion I need raspberry pico 2040 (or similar with minimum 512KiB ram) because have more ram 

for example ruby or other language. this device must run many protocol many network therefore softweare is very importantn (tnc, direwolf linux etc.) Why not put screen and small keyboard? Simple keyboard similar old cell phone.

Second question is wire. why not put mic and audio output? for example for dewice without any input source audio. ok this is not good but if You dont have any device but have normal radio or walkie talkie without connector?

look this https://www.adafruit.com/product/4074

and http://www.whence.com/minimodem/