I don't see how owning a lot of Bitcoin gives you more say over the network this isn't proof of stake, If that's just to have X allocation, with a fork seems like a waste of money, you could just fork it right now and give yourself whatever allocation you want.

If you fork based on the current chain state, you give a lot of people an allocation in a coin/chain that the US government might not want to enrich, why would Blackrock want to give El Salvador, Bhutan, the Lazaras group and all other so called unfriendlies more funds? Just like Blackrock can dump so-called legacy Bitcoin, others will equally dump their BR-Bitcoin

If you fork you can't just port the lindy effect of all the businesses, developers, wallets, software, miners, protocols and users over to your network, you can fork but you're still bootstrapping a brand new network, and good luck to them, many have tried and failed

While blackrock can try, they about making money and reducing risk, just buying their KYC bitcoin and shutting the fuck up is going to get them further in terms of income and AUM growth than what you're proposing, so if you believe blackrock turns from being incentivised by money to becoming some idiolog that just wants to waste money failing to take over a network, thats a long shot in my opinion.

If you're worried about these things you don't have the conviction in the Bitcoin thesis and incentive structure and it might be best to sell down your stack to a point where you would no longer be worried.