[Asterisk-Dev] Another weird dialplan question

[asterisk at funkspiel.org]

OK, here's another oddball question for y'all:

Is there a way you can force all calls to go to a certain extension
before they exit?  I mean something besides the brute-force solution
of making sure every end node in your dialplan is followed by an
explicit Goto (and doesn't call Hangup first!)  What I want is
something like a Java-style "finally" clause for your dialplan.

I'm almost sure the answer is no, this can't be done.  (I've read the
O'Reilly book, for instance, and it doesn't mention this feature).
However, I want to be 100% sure before I start hacking, because my
current dialplan is going to be much more tricky without this feature.

Speaking of "you can't get there from here", what would it take to
write a replacement for Asterisk's dialplan-processing engine?  Am
I crazy even to think of this?

In any case, thanks.  So far your answers have steered me down the path
of wisdom, and away from the path of madness. :)