I noticed that there is a Public Category for pages that can be edited by anyone. What if there was a Template for those pages specifically saying that editing the page is allowed for anyone. It is not easy to tell a page is public by just looking at it unless, you look at the categories, but then some people don't even know that category exists.
It would probably look like the Mature Content Template and could just say something along the lines of," This page is owned by ___, but its is public to editing from anyone." Then there could be an option to add custom Restrictions to the label, that say None as a Default. This is encase someone doesn't want specific things changed on the page.
I honestly don't even care if it is exactly as I described it, I just thought it would be an okay addition, even if people won't use it very often.