Of course the only thing protecting bitcoin from losing its MC status is the block subsidy, so there is real risk that over time bitcoin could cease to be the main chain.
so then you're effectively saying we have to have inflation in BTC for the Bitcoin MC to survive/compete over the long run when put up against a SC issuing a sidecoin and accepting scBTC.
i don't desire that and i certainly don't want to be moving my BTC to a SC.
You either risk a side chain overtaking bitcoin or an alt coin overtaking bitcoin. With the side chain you have the risk free put to take advantage of if the side chain wins out. The alt coin would have a harder time winning without the risk free put, but it could happen. Pick your poison.