1) it's not really my call, I just hack the window manager; this is something the HIG people need to figure out. But
2) notificationisation and minimisation appear to me to be functionally very similar and I don't see why they should both be supported
3) if only one of them is supported it should presumably be the one we've been using for the last few decades rather than the new one
4) but it might be really useful if we allowed people to add options like "stop" and "rewind" and so on to the right-click menu on libwnck (the task bar) and the right-click metacity menu, via EWMH.
In any case, we still need to discuss this on wm-spec-list.