Hi Max, I am sure that you are under heavy load now but I noticed an issue.
I have a Oneplus One with latest Ressurection Remix ROM and on build 588 I could utilize the rom's function to control playback with volume buttons with locked screen.
I haven't updated the rom but I installed the 705 (same on 706, 709) build and the playback control doesn't work for PAMP (for other players it does).
Also doesn't work with offscreen gestures.
Could you please check the issue if you have time for this? Maybe it would be helpful so that it doesn't end up in the final version.
Thank you very much for your support and thanks for Poweramp. (Using since Symbian)