arbitraging the bitcoin market is about manipulating the market.. it has nothing to do with the PoW mechanisms of mining and changing the blockchain
emphasis TWO SEPARATE THINGS

..
YOUR whole premiss was that you want to manipulate the market purely by changing blockchain data.. but you have avoided, ignored, dissmissed and been not convinced of all the mitigations of the blockchain attack vectors you discussed.

and you also did not understand:
the real world timeframes of doing one thing to realise if it would help or hinder the other thing
the real world affects and limits to effects of one thing on the other
the real world costs of one thing compared to the other

you did not sem to actually want to play out any theoretical attack and see if it actually results in a market manipulation. instead you just posted some lame theories hoping to find some ethereum shills to blindly agree and pat you on the back to pretend that ethereum is better without any actual knowledge or thought

it seems you just want to pretend bitcoin can be attacked easily by ethereum, but you have not gone into the research depths of even trying to prove a point