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They vote with their CPU proof-of-worker, expressing their acceptance of valid blocks by working on extending them and rejecting invalid blocks by refusing to work on them. Any needed rules and incentives can be enforced with this consensus mechanism."
- S. Nakamoto
The question to me is: What exactly is an 'invalid block'. The final protocol could be very flexible here. Major rules should be: 21 Mio fix, no double spending,... ??
Well, in a decentralized system, the rules could be anything. The miners have the power to set them to what ever the majority of them want. We, the users, merely have the power to either participate or not participate.
As for me, the two rules you mention are indeed dealbreakers for me. If ever they become violated, I will not participate. As would, I imagine, the vast majority. Which is the only power offsetting the miners' greed.
So far, so good on that point. And I imagine shall always be.