I am using P3Dv5, FSLabs and all jet PMDG aircraft. Not sure what you mean by functioning PTT but there are RAD/INT or MIC/INT switches on the radio management panel. They are animated but doing nothing. I am too far away from programming and for me lua script or lvar are just strange words, but I know using mouse macros one can assign a key or a joystick button for pretty much any button or switch in the VC. So my question is, is it possible to make that working in a way round, you press a button in VC and it sends a key press? It also may find application in using UGCX from FS2Crew, they are also offering hotkeys for initiation, PTT, mic mute/unmute etc. So you can bind RAD for vpilot and INT for UGCX.