This could be very, very good. And it would certainly make it a lot easier to maintain a thread/discussion/whatever without having to clickety-clickety-click around with the mouse just to perform basic actions, like replying. And 1+2 is definitely what I'd like to see eliminated.
I think the timer handling should be implemented to allow for less "screen noise" (pop-up) for those that have learned META commands. So if I press ESC G H in rapid succession, I don't get to see the menu pop up at all. But if I wait for, say, 0.7s between ESC and G, I would get the full META menu, if the input timer expires between the G and the H, I would get the menu, and have the selection bar be positioned on the Group commands.
But either way, if we get the META "system" implemented, I think we have come a long way towards a more efficient interface.