I'm not sure where this PoS "collude" concern come from. Who would collude to destroy their own wealth? I hold some peercoin, if you tell me to collude with you to attack Peercoin, I would tell you to gfys. Do you think it's easy to collude with 10,000 peercoin holders? or is it easier for discus fish and ghash.io to collude? I think the answer is obvious.
You seem to have missed the IPO idea of creating a PoS with say 21 BTC and a bunch of anonymous bitcointalk accounts (do I need to name the coin?).
It is perfectly easy to collude to gain 100% of the initial distribution if the cost is so low (but maybe very expensive for anyone else to *take that away from you* once the coin *gains value* via an exchange especially if the "initial stakeholders refuse to sell").