regarding the concensus algorithm, we'll decide collaboratively over tau. it'll begin with some mechanism (which doesn't really matter) and evolve into what we make it
Is there a fast way to replace standard PoW consensus mechanism? (as one scenario of many others) Miners could threaten to attack the system if the community will dare to start a discussion about replacing the consensus mechanism
if the concensus algorithm is able to change itself then it's inevitably not-exactly-pow, and to determine to which extent it's mutable and still keep the basic network premises, is to be done collaboratively. there is no one answer and the answers should be taken in broad concensus regarding proven truths over tau.