Mistake 1 : Sidechains can protect the value through merged mining.
inherently less secure and encourages mining centralization. best case expect a MM of 50% that of Bitcoin. that is insecure. see
https://www.reddit.com/r/Bitcoin/comments/2k01du/peter_todd_on_twitter_the_sidechains_paper_is/clgpjpx
Mistake 2 : A chain that has greater value than Bitcoin = an alt-coin with greater value than Bitcoin. Utility features/services annexed to the main blockchain DO NOT have greater value than Bitcoin, only an alt-coin (supported through a sidechain or not) can claim this. If that is what you are suggestion (altcoin taking over) Sidechains are NOT introducing this risk and do little to enable it. As smooth has pointed out, the creator of such an altcoin would realize it is not necessarily desirable for his coin to utilize a sidechain.
wrong. you just ignored Adrian's model of declining BTC fees paid to Bitcoin miners, a result of ppl moving to scBTC b/c of the risk free put and innovation. all the tx fees will migrate to the SC leaving Bitcoin miners no choice but to defect over the long run.
Mistake 3 : Assuming the transfer of scBTC does not generate, by proxy, the movement of economic energy to the main blockchain.
the correct way to look at this is you are breaking the link btwn the MC and its BTC by moving highly secure BTC to relatively insecure scBTC. the equilibrium price of BTC will go DOWN.