I think you can do this relatively simply with infrared led lights. Imagine "Please don't kill me" remote controls. You are a bit more visible when broadcasting, but presumably you can be selective when turning it on.
Then we need to ask what happens if communication itself fails? An enemy that knows you are doing this has incentive to jam Communications. Either you do nothing in that case because there might be something you can't communicate with, or you kill your own people
It's not perfect, but it's cheap and it should work.
Give me a couple hundred k and I can probably build the prototype, haha.
The idea being that there is no communication to jam because the drone is fully autonomous. Given that, one needs a foolproof way for it to identify the enemy.
In this case the absence of communication would be what gives it permission to engage. Jamming the drone would not save you, but you could potentially make it attack its own forces if there happened to be any around at the time it comes for you. An IR beacon would make that very hard to accomplish.