sure!
NO
How? well, first you make the change to the protocol and the market does the rest.
so my question is is it possible yes or no?
my answer is categorically NO.
it is not black or white. it is also yellow, green, purple, orange, red.
in a sidechain world, value resides on multiple different chains that operate in synergy. miners will mine wherever there is value. when you consider that the 5% you are referring to might translate to millions of dollars I don't see any reason for them to abandon that revenue stream since it is trivial for them to support it.