If this is his aim to centralize Bitcoin mining and change the POW structure to something else, then it wouldn't be possible since in the end he only owns some few nodes while other miners scattered all over the world would continue mining Bitcoin honestly. In case he chooses to become a dishonest miner, he wouldn't be able to convince every other miner to join him and even if he bribes some dev to try a hard fork and create a possibility of mining Bitcoin off chain, then they would only end up creating a new token which would still prove worthless in the near future.

Bitcoin is fine as it is and on-chain transactions is the best and most secure way of using Bitcoin. I wouldn't settle for a less secure, customized  off-chain activity.