[Deskbar] Unavailable handlers in prefs?

[Mikkel Kamstrup Erlandsen <kamstrup daimi au dk>]

Id like to change the prefs dialog so that there is a way to discover
handlers purged on startup. This should also show the error messages
returned by the "requirement": field of HANDLERS.
Currently there is no way for users to discover any slumbering powers
within deskbar...

I don't know exactly how to do this without taking up to much screen
real estate or clutter the prefs dialog. We could use two tabs
"Available Handlers" and "Unavailable Handlers" or something like that. 
We could also use an expander but it doesn't fit that good in the
current layout.
Then there's an external dialog (activated by a button in prefs)...

Any other ideas? What do you guys say? - I got a feeling that this idea
is not going to be popular :D - Maybe my GUI intuition got screwed by
too much debugging...

Cheers
Mikkel (aka "The deskbar-applet-list Spammer")