I've thought about similar techniques (mainly a static redirect for all reddit links to a read-only archive, as a browser plugin).

Technically speaking, this is mass copyright infringement, unless it happens to fall under fair use. Reddit wouldn't have standing (for content its admins didn't create), but every other user would. I can conceivably see a copyright suit being granted class action status, and Reddit (who does have a vested interest, even if they had no standing) bankrolling the whole thing.