automated index suggestor -- request for comment

The manual is pretty sparse on advice regarding indices. Plenty of
good feature documentation, but not much about when and where an index
is appropriate (except a suggestion that multi-column indices should
be avoided).

Of course, the ultimate arbiter of which indices are used is the
planner/optimizer. If i could somehow convince the optimizer to
consider indices that don't yet exist, it could tell me which would
give the greatest benefit should i add them.

So, i'm writing for two reasons. First, i want to gauge interest in
this tool. Is this something that people would find useful?

Second, i am looking to solicit some advice. Is this project even
feasible? If so, where would be the best place to start? My assumption
has been that i would need to hack into the current code for
determining index paths, and spoof it somehow, but is that possible
without actually creating the indices?

Any and all feedback welcome.

-johnnnnnnnnnn