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.
P2pool is a good alternative, but hacking is actually far from my biggest concern. My biggest concern with PoW is that continuous non-stop transfer of wealth from the Bitcoin community into the pockets of mining hardware vendors and electric company. This I believe is the biggest reason we are seeing the strange price action this year, with massive amount of good news and adoption, the price keeps dropping. I think this is due to the inflow of capital can not keep up with the insane mining cost (and wealth transfer rate out of the Bitcoin eco-system into the pockets of hardware/electric companies).
Can you imagine, if these hundreds of millions of dollars, instead of spent on pointless PoW mining, profiting the hardware/electric companies, if these money are directly invested in the Bitcoin eco-system, what it would do for Bitcoin?