how do you know a brand new will be effective even if it is vetted by devs? only with use, time, and multiple hacking attempts will you know definitively. otoh, you know for a fact that a MM rate of say 50% that of the Bitcoin network will cause a decrease in security for the SC. the market will price that in even though you won't.
so naive.
read above for the first part of your question.
as for MM. I expect the MAJORITY of miners to support an utility sidechain putting forth a significant feature that should attract considerable use and therefore profit for them.