ok lets look at this deductively.
The only way to flood services is on IRC or off IRC. Nothing we can do about flooding off IRC so it's out.
That leaves on IRC. Session limits, IRCd sendQ/recvQ and build in clone limits handle the single user flood. That leaves multi-user (drones) flood and the only way to stop a multi-user flood is to ignore everyone and that is what DefCon2 is for.
Let's face it, if you make services ignore the attackers drones even with a per user services sendQ/recvQ, they will simply load more. The already existing DefCon solution is better than any anti-flood module could be.
[Edited on 8-5-2007 by katsklaw]