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If this is already possible (as the commenters talking about PHP claim), then perhaps the question is just one of publishing some documentation that explains how to do it for other mixtures?

I did pay, and I'd gladly pay again, for this :).
Seems like it's actually working now.  Did this get stealth-fixed?
This strikes me as a specific instance of the more general problem that ST2 doesn't link against the system Python on Linux.  Of course, in order for that to work there would have to be specific packages of ST2 for each platform, since each distro builds its own, and may have different versions...  Still, that would be great, and it would make the binary smaller :).
The effect is similar, but not exactly the same... for some more explanation of the usefulness of finding out what the command would be without necessarily executing it, see
Not just the sidebar: being able to set per-project settings via an API would provide for a way to alter the behavior of a window without having to scan every view in it and try to keep those settings variables synchronized.
There are contexts where the view *should* be None, although it seems like they aren't being queried now.  See

Maybe it would be better to have a different method for these "limbo" keybindings?
As long as we're talking about plugin development - it would also be really handy for the describe-key [i.e. C-h k] equivalent to also display some information about why a key was mapped.  In a few cases I've been confused as to why Sublime chooses one key over another when both of their context conditions are all true, or what plugin has decided to map a particular command.
Absolutely.  I've been able to get Sublime's keyboard input to react exactly as my fingers expect (given 15 years of using Emacs heavily), but C-h k ("tell me what this key binding does") and C-h w ("given the following command, tell me where it is bound to a key") are impossible to replicate with Sublime's current API, as far as I can tell.  It would be great to remove that limitation.

(Although I should note that sublime.log_commands(True) comes very close to the former.)