I've been mining for about 4 years now (1btc/month and 35-40eth/month since March 2017), and this is the first time I've heard someone trying to say PoS would lead to MORE decentralization. To be fair, I don't regularly converse online with other miners. I mean, I see what your arguments are here, but I'm just not sure I agree.
Usually the only people trying to promote PoS are the ones who are financially well-off enough to buy the masternodes. You could make the same argument for mining -- to do it on any worthwhile scale you better be prepared to spend a minimum of $500k -- but "worthwhile" is subjective, and some people are fine only making a residual income off of their mining, because they feel like they are contributing to the "cause" -- to keep the network flowing -- amongst other reasons. Initially, I got started with mining out of pure idealism about decentralization, anonymous currencies, and the cypherpunk roots of it all. That turned into me making significant investments to mine on a larger scale. Maybe people doing it for those reasons will be less important as time goes on and it's more mainstream...I don't know.
My other business is legal MJ cultivation in California and Michigan, and it's the same thing in that industry -- the only people wanting, or not minding, the expensive licensing and startup costs in California are the well-financed companies who can afford it all, who can wait many years for profits if necessary. Everyone else wants a way for easy entrance in the market, low licensing costs, etc.
As for government interference, I was a "traditional market" operator for ~14 years in the MJ business, and have experience with avoiding scrutiny from the government. In fact, the issues with bitcoin mining are identical to that of growing marijuana on a large scale -- exhausting large amounts of heat, the intake of large amounts of fresh air or cooling BTU's, using large amounts of electricity, the need for good airflow in the facility, etc. With that said, you could structure your mining operation so that only a very targeted, focused investigation could find you -- it wouldn't be easy to "fish" and find it. For example, the main indicator would be the electricity usage, but there are tons of legitimate businesses that use far more electricity than a mining operation. Establish a business that is in that industry, buy a warehouse for that purpose, get your electrical installed, and then run all your miners through your own VPN or Tor (I've never tried to run them on Tor, because I was always worried about speed/connection problems.) They would see large electrical usage, yes, but that is normal for your registered business.
In this hypothetical government overreach scenario, hiding a mining business -- if you really had to -- wouldn't be any more difficult than hiding a large scale grow operation, or a meth lab, or anything illicit really. You just have to know what you are doing, but people have been doing this for decades and decades without problem.