I don't know if someone have already suggested or asked this but ...I'll ask anyway...
Why don't you make these widely used but "unofficial"cachetypes official cachetypes or subcache types for unknown caches, for example
- caches where you can find pieces of coordinates from other cache or cache series
Or if not official at least possibility to use different colored question marks for those in geocaching map so they would be more easy to find or pick up... ;
Bonus caches, yellow question mark; challenges, red qestion mark; etc ...
found old thread related to this (http://forums.Groundspeak.com/GC/index.php?showtopic=308226&hl=bonus&st=50), but I'll let this still be here because that suggestion of using different colored question marks is something that would be a new feature?