I agree that nothing would change. Even the "flushed to journal" approach of databases and filesystems would remain, because that doesn't just happen because of

I agree that nothing would change. Even the "flushed to journal" approach of databases and filesystems would remain, because that doesn't just happen because of the looming danger of power loss, it also happens because software malfunctions exist and you want to separate work in progress from the done and approved. And if it's not cheaper as RAM it's not interesting anyways. Chances are if you could afford 1:1 paging plenty of applications would happily do and not mind the separation between a fast copy and a persistent copy at all.