Then sidechains become useful only for trivial sums where one is willing to accept the risk of loss, confiscation, or theft.  This means Bitcoin primary chain remains superior and sidechains don't provide a 'fix' to scalability.  To we are back at square one.   

As far as implicit trust 'solutions' a centralized third party (i.e. coinbase using off-chain transactions) over anonymous entities (i.e. federate trust pegged sidechains).  Both are inferior to a trustless model but at least the actors in a large centralized entity are known and have something to lose.  Far too easy for the anonymous entities in a federated trust to collude and abscond with the 'locked' bitcoins without any risk or consequence.