ah, that does make sense actually. but what happens if, as it becomes clear that a SC is going to win over Bitcoin, miners begin to jack their mining tx fees just b/c they can to create the SPV proof tx required to make the switch to scBTC?
also, there still is the question of Blockstream creating an additional asset on the winning SC ahead of time that stands to profit from a rush of BTC to scBTC.
I understand you are trying to poke holes into the concept and it is legitimate to consider these ideas BUT to me, suggesting that a SC is going to win over Bitcoin is essentially the same as entertaining the possibility that an altcoin would take over. The chances are slim to none, for the innovation required by this SC/alt would be so considerable that if we do reach this point, then to me it simply makes sense that Bitcoin core and their developers will recognize the innovation and adapt Bitcoin accordingly.
I don't see the advent of sidechains bringing forward fundamental, competing, money-function blockchain. I think it is Risto or Aminorex that said there are only two liquidity market currencies can compete for : legitimate and dark market. Once one or two have established their dominance over these, any additional feature is superficial and will not attract anything more than situational/speculative use.
I see sidechains as application specific uses of units derived from the Bitcoin ledger. IMO, any attempt at creating a sidechain that will compete with Bitcoin's money function will fail the same way alt coins have failed.