I'm as pro PoW and anti PoS as anyone, but your case is not strengthened by the sloppy reasoning at the end:
In proof of work, when you setup your ASICs and start mining you're, intentionally or not, subsidizing decentralization as the rest of the miners suddenly have less power.
The same thing happens in proof of stake: To acquire voting power you buy stake from existing stake-holders, who end up having less power.
The opposite happens in proof of stake: To acquire voting power you increase their gains.
Financial gains has little to do with it. If you buy ASICs from another miner, then you also increase their gains.
This.
I am not aware of any serious argument that suggests PoS will result in mining to become centralized, over time or otherwise.
Bitcoin PoW mining today is not controlled by any single entity, but the number of major miners has decreased from what would have been predicted even a few years ago. There have probably been times in which a small group of unrelated entities could theoretically band together to execute a 51% attack on the network, but the economic incentives around PoW seem to have held up and we have not seen that.