My point is if you want security to be in the amount of people who participate then you're moving security to the edges. The truth is, if you have good economic incentives then the behavior of the participants will at least in theory conform to protect the security of the network because it will be in their best interest to do it.
Mining isn't really going to ever be decentralized on the level of everyone being a miner is my point. That is a false possibility in the first place. I'm not sure anyone seriously believes grandma will be mining Bitcoins on her smart phone along with billions of people in developing countries. We have to at least be realistic about what is likely to happen and that future is extremely unlikely.
In my opinion the security of Bitcoin is based on the structure of economic incentives, not the amount of hash power miners generate or how many miners there are. You can have security with Proof of Stake greater than Bitcoin no matter what the hashrate of Bitcoin if the Proof of Stake has a better incentive structure.