To put it in a simpler singular perspective, on the guitar you would need two transmitters and one receiver, and a suitable battery capacity to run those and the guitar modelling circuit.
On the other end, you would require two receivers and one transmitter, so the cost would be roughly 3 times that of a regular wireless guitar system.
Then to make it cater for all, a cheepo short range 2 hour charge system won't do, it would need to be acceptable at the (semi) pro end too.