i've given you a very plausible path to a scenario that could hurt Bitcoin. you can choose to hand wave it away, but i know human nature and if there is money to be made, ppl will go for it. especially since they are in a for-profit company with a financial guy like Hill. that's not a personal knock against him; it's his job to go for it.
this thread isn't for sticking your head in the sand. we flush things out here.
I'm sorry but it is not a plausible scenario.
This is open source software. Even considering stealth development of a rogue sidechain, the moment they commit the code to a sidechain, the code is out there for everyone to see.
You propose that once this happen, the traction and network effect of this sidechain is so fast that Bitcoin core can not adapt in face of a supposedly paradigm shifting implementation of crypto. Again, I'm sorry but this is a losing bet.
There is already ENORMOUS money to be made by Blockstream while behaving in a community-minded, responsible way. Surely Hill is not trying to rule the world. Imagine Blockstream becomes some kind of RedHat for Bitcoin. Well my guess is he doesn't even dream of this measure of success.
The economic interest you are putting forward in your previous post is a considerable RISK considering the open source aspect of crypto. They stand to lose their credibility, their carreer, and more if they even attempt such scheme. In reality, apart from a couple more million in their bank account, there is NO incentive for anyone in this group to behave like you suggest. Considering they already stand to make millions by having a stake in and improving the Bitcoin economy your scenario is a most farfetched one.