Like, if miners that control > 50% of the hash power come together and decide they want to increase the reward per block mined to 100 BTC, couldn't they do that?
Since it's all peer to peer they could just change the software to accept that.
I believe that would require really foundational source code changes and would cause a fork, meaning it would become a different blockchain...it would no longer be bitcoin.
The best way for this never to happen is we need more mining pools