Hi, I like idea 1+2+4! This could also help to find rare files and group similar files and it's traffic together.

I didn't get the advantages of number 3, sorry. Hmm a super peer could throttle routing searches instead of sending them immediately, then group searches from various clients and send them out together to avoid querying for the same file multiple... however a search cache in servants and superpeers does the same, reduces traffic and makes requerying not that unhealthy.