let's say those 2 factors balance each other out exactly, ie, half of BTC holders convert BTC to scBTC while the other half stay put and half the miners currently mining BTC switch to primarily mining scBTC. in that case, then i say the Bitcoin MC still loses. which is really the risk i'm trying to identify, that being any damage a SC might inflict on Bitcoin MC. it loses b/c the SC has succeeded in weakening Bitcoin's security by 50% subjecting it to possible 51% attacks and volatility (which will happen if any weakness in Bitcoin itself is detected by the market). as volatility picks up, the price will drop.
not true.
using your base case. you have now essentially created two liquidity market. a transparent ann a private one. these are the only two markets that can work in synergy. both could thrive without effectively damaging the other. as long as people find value in transparence and in privacy and there will be a market for both such market.
I actually believe this is something that could very plausibly happen.