I'd argue PoS miners are much more security minded, since they have to pretty much keep the wallet hot (online), even if briefly, in order to mine with it (though I believe in DPoS system you don't have to, since mining is delegated to the delegates, you can put your funds in cold storage). Also they are very much de-centralized, instead of concentrated in a pool, can you imagine how hard it is to obtain the identity of 10,000 PoS miner, their IP address, and then some how access their mining PC etc...
Being more security minded is not good enough. Good security is both difficult to achieve and hard to maintain even with security experts. What we need is a protocol that is secure intrinsically by several different methods by its innate design and not dependent upon how careful the users are.
I'd be much more worried that discus fish and ghash.io getting hacked simultaneously (imho a much more likely scenario) and the attacker instantly gain 51% in Bitcoin.
This is a valid concern and why I suggested that your proposals are 1 step forward and 2 steps back. Mining centralization should be addresses by incentivinzing p2p pools and gettig more involved in mining, and a greater adoption of full nodes.