Well, in this case another attacks vector is possible - creating fake evidences. Unfortunately, authors of all proposals like that dont' describe details, so it's hard to propose concrete attack.
It is impossible to create fake evidence - you will need the private key of the pool's owner. 2 digital signatures of the same pool for 2 different blocks at the same block height are the evidence. The same block height must be digitally signed twice by the pool. No one can do this other than the pool's owner.
And why pools are needed? Evidence could be published against concrete forger. Pools are adding unnecessary centralization imho.
Do you have details on how to detected and publish evidence against concrete forger? As I explained in my initial post I don't think it is possible if a forger does not have to sign each and every block. I have not seen anything concrete so far. You'll need pooling to put all stakes into each and every block and detect double-voting.