YOUR whole premiss was that you want to manipulate the market purely by changing blockchain data.. [...]
It's not really 'market manipulation' in any way. It's more like an 'adversarial exposure of a security flaw in the technology of a competitor,' and arguably 'sabotage' if they really go through with a full attack.
[...] but you have avoided, ignored, dissmissed and been not convinced of all the mitigations of the blockchain attack vectors you discussed.
Name one mitigation strategy that you have mentioned above on this thread that isn't either 'extending the confirmation period,' which as I've explained doesn't really seem to help much since it cannot be done retrospectively, or would mean a departure from pure PoW, which would be a remarkable option as it would go against Bitcoin's protocol as is.
Also if you like, feel free to mention any other interesting ones that you can think of, as this discussion was the main intention behind this thread.