How would you mount a wireless mic pack like this one
to guitar without damaging the guitar or impeding the player?
[EDIT] oh and the strap is not preferable!
I've put a pack on an acoustic before in Theatre, you just provide a new strap and sew an elastic pouch to it. Run the cable down the strap and tape the mic in place / jack plug.
Obviously easier to do when you have a wardrobe department available, but shouldn't be to hard.