There is a simple way to relieve some stress of servents with no free upload slots :

Don't make them send out anny responses until upload slots are availble .

Now responses going trhu the servent will be unaffected ofcourse .

Allot of servents have auto-retry features including LimeWire .
Ive seen my LimeWire "under attack" of 17 different servents that tried to upload from me every 60 seconds .
Annoying to the least .

It would also reserve bandwidht on the network .
-less search results have to go through the network .
-Less bandwidht is waisted on servents tryng to make file tranfers off full servents .

Also this would be easy to implement since no changes have to be made to the protocol .

I deffinitly see this coming in future versions unless someone can find me a negative side of this idea .