I'm an original AeroflyFS user and soon to purchase version 2. I've been following the progress closely, and I love that you've added VR support. I see that ATC is on the development road map, which is great.
Anyway, my suggestion for you with ATC is to start simple with background ATC chatter. It would really add to the immersion and be fairly simple to implement as a feature that users toggle on or off. Perhaps you could license these sound files? http://realatc.net/ They are really good for the USA (with a few for Europe). I use them with ProATC-X for P3D and can highly recommend.