Hi Chris,
The BT transmitters will certainly do the job of piping audio from the PAW 3.5mm jack to a BT headset and if you're 'normal', as opposed to me, then it's a great solution. I've got one and they work
My problem is that I will be mounting my PAW behind the panel and it will be less accessible than normal. I will have my PAW powered from a Charge4 USB charger and have the spare port to ensure the BT transmitter is charged but the problem comes after a flight. When the aircraft battery switch is turned off and I walk away from the aircraft then the BT transmitter will still be plugged in to the PAW and the battery will wear down as it has not been specifically switched off. Fast forward a few days and I'll switch everything back on, the USB charger will provide power to the BT transmitter BUT I will actually have to turn it on again........cue clambering beneath the panel which I hope to avoid with a different audio solution.
If I could wire the BT transmitter permanently on then it wouldn't be a problem as it would only work when it's plugged into the USB charger and that would be fine with me. I've had a look at the little box and it's sealed up rather well
If it didn't need switching on again once the battery has worn down then all would be good, but this is not the case.
The BT dongle you linked to earlier would do the job IF PAW audio could be piped through a USB port. Yes, it would mean the loss of a USB port but I could live with that
If that doesn't work then I'm more than happy to buy a Pi 3 with built in WIFI and BT and hopefully get PAW audio through the Pi.