Is there or will there ever be a way for people who aren't the owner of a directory listing, to flag that site as dead and request to have it removed from the directory?

It sucks to click on a directory link that looks exciting and see that the site is either in maintenance mode or deleted entirely. Recent bumps generally help to indicate activity, but sites that go a long time without bumps aren't necessarily dead, it might just mean their staff aren't active on PP.