making lookups from exmh address db smarter

I've got exmh configured to automatically add address to the address database. 
I like this feature very much, but a consequence is that the database is quite 
large (17724 entries at the moment). Lookups are reasonably fast, but it would 
be a huge improvement if the results could be weighted by time or frequency.

For example, I'd like to sort search results with the following algorithm:

	if there's one exact match
		display that

	else
		sort matches in order of preference by:

			matches to addresses with correspondence within the
			last $TIME_INTERVAL_USER_PREFERENCE

			matches with number of db entries over
			$FREQUENT_CORRESPONDENT_USER_PREFERNCE

			all other matches

This way, if I enter a name and it's close to someone that I have 
corresponded with recently or often, the addresses of the frequent 
correspondents are shown at the top of the list.

Any suggestions about how I could implement this and contribute it back to exmh-
-or has anyone done anything similar?

Thanks,

Mark