An Index Scanning Solution question

Hi all!

Earlier I sent a question about multi-order index scanning
(http://archives.postgresql.org/pgsql-sql/2004-04/msg00276.php)
I can solve the problem with own OPERATOR CLASSes. But this solution
increase number of my indexes exponentially. In my applicaton I have
already more then 200 indexes on a table with 500 000 rows. I will have
1 000 000 records at the end of this year.
I'd like to ask why the index scaning can't move on an index in
multi-order directions (For exapmle: 1.column: forward, 2.column:
backward and 3.column: forward again)? So I wouldn't have to use so many
indexes. Has somebody tried to implement this idea in Postgres or is
there a more difficult reason in the postgres implementation which
cause this defect?

Thank you in anticipation!
Antal Attila