I'm not sure, but isn't it possible to launch some commands in vlc just knowing its PID ? In this case, a program specially designed for the desired environment could be created, using hooks...
Another problem whit global hotkeys is multiple instances : for my part, I usually let more than one instance of vlc opened, with just one playing sound or video. With global hotkeys, how to know which media to play/pause ? Conclusion : global hotkeys means unique instance.
Nevertheless, I also think that it's possible to create plugins for vlc. I could create something wich works with windows/gnome... Even I never created plugins for vlc, and I'm in exams... So, be patient.
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