Turns out that if you intercept the USB communication between the Fly app and the controller you can pretty much do anything regardless of DJI support for it. This is still a work in progress as it still needs a first connection to the smartphone, then it's possible to inject (and receive) almost anything, power level, gymbal control, raw sensor data, and maybe more.
Currently using a PI4 as the MITM host but I'm working on migrating it to a microcontroller (esp32-p4). Data can be forwarded via LAN to a remote PC/Control station. #technology