But I still dont see how you are stopping individual miners. I guess you're just focused on controlling mining pools.
We are not stopping individual miners but only limiting the hash computation to a group of miners at each block.
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You didn't address the question about what is stopping an individual miner from just setting up a bunch of private keys and doing that hash on each one to guarantee they get a favorable hash result from at least one of them. They would most likely do that. So you must not be worried about them cheating the system in that way. 
If individual miners would do that then you can get dollars to donuts that larger miners would too somehow.
They can do that. But it will create for them the issue of managing a long list of addresses and keys. And that each time they will need to spend time calculating the signatures and the hashes. Which at the end may not worth it. If individual miners would do that then you can get dollars to donuts that larger miners would too somehow.
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Which is why I doubt we would ever see something like this in bitcoin. Miners control the game. And they seem pretty happy with the way things are.
Yea. But this is NOT a desired outcome. Because we have a system that was supposed to be decentralized became de facto centralized in the hands of few miners. What if these few miners decided to engage in 51% attack without announcing it and steal people money.Quote
Well I wouldn't know that I agree with you that miners would be forced to share their private keys with each other to work your system. For example, what's stopping a group of miners from creating a multisignature taproot public key? i guess it's a theoretical work around but maybe not so doable in practice hopefully for your sake!
The idea is to create a system that is as decentralized as possible. The current state of affaires is not at the best interest of Bitcoin ideologically. Today, we have few miners running the show and they can create a monopoly whenever they want to. Just another Banking system with a different name.