For once, this isn’t about an existing bug– well, there’s a tenuous connection to GNOME bug 311428.
Several of the recent squibs have resulted in the observation that an external script could be made to do the work. This is true for responding to keypresses, but for problems such as performing some action whenever a window opens it gets a bit harder– the external script must run all the time and either monitor X events or, as devilspie does, get libwnck to monitor X events on its behalf.
It might be a better idea if Metacity (or libwnck) could be given a list of commands to run when windows open, and possibly on other events, to make writing plugins easier.
The (fast!) default would be the empty list, of course.
Another event which it would make sense to be able to tie plugins into is window role change, so that a window-matching script could learn automatically.
It would also be sensible to allow programs to be executed when mouse buttons other than the main three were pressed (so you could launch an Exposé clone by pressing the shoulder button, for example).
Photo © Katie Sutton, cc-by-nc-sa.