How about instead of using some hypothetical situation that has nothing to do with reality, why not instead figure out how things actually work now and go from there?
The reality is that there are anti-BTC entities. There are also big miners. At the right price, big miners may sell their mining hardware to anti-btc entities.
You had mentioned an entity that owns lots of mining hardware. I agree that is a problem.
Suppose there are multiple such entities now, BTC will be in trouble.
This is a key issue. Mines amounting to >>51% could be sold, without public knowledge, to the same anti-bitcoin entity with deep pockets and that's it 60, 70 +? %.
This problem has now surfaced for real and will continue to be a drag on upward Bitcoin prices unless something more substantive than an untrustworthy mega pool making an announcement saying that we should trust them is made.
or
The whole point of Bitcoin/Cryptos is that trust is enforced by the protocol/network/system...this is currently not the case. This problem needs to be solved in some way at the protocol level or upward price movement will falter as people lose trust / get nervous.