It sounds like it should be possible, but I've never done anything like that.
To me, it sounds like lots of work just to use a standard guitar cable when there's nothing standard on either end of the guitar cable...
Standard phantom power for a studio microphone is sent common-mode over a differential (3-wire) connection, so that a standard dynamic microphone never "sees" the voltage across it's coil. 9VDC accidently plugged-into a standard guitar pickup, or into a standard amp or pedal probably won't damage it, but it might be better to play it safe and use a different connector.
And if you are going to use FM transmission, I'd stick a battery in the guitar and go totally wireless.