1. Everybody sees his transactions are not processed or a lot of double spending.
2. New thread will start @ bitcointalk :-) (why my transaction are not accepted ... reason will be found.)
3. Pool's operators will say "we do not do malicious things if you believe us then accept block with this signature".
4. Some anonym operator/miner will do the same. This is my public-key. (you do not have to know his identity)
5. some group of honest miner will formed.
6. You can see who broadcast bad blocks or do not provide signatures.
7. New client is released ... you can configure what signatures you will accept.
8. you can choose new group of miners ... or use old one, but that is malfunctioning.
... majority will be formed :-)
That in fact was implemented already and is called Ripple Because that's basically replacing the PoW with a trust network.
I'm not sure you understand what I'm talking about. (I'm not native speaker)
Edit:
It is Proof of Hashing Power in case malicious entity has 99%. :-) (I'm a little drunk)