If I have a page with slug "my-impt-petition" that I set as the front page, that page will then no longer be accessible via the URL my.nationbuilder.com/my-impt-petition

This is no good. I could have totally have linked to the page previously and thus broken all my links. Worst case scenrio is I send an email to gobs of people with the link right before I make it the front page, ensuring the failure of my email outreach.

The best thing to do would be to make sure the front page can still be accessed via it's slug.

If that is problematic for whatever reason, then permalinks that can be depended upon should be prominently displayed to admins. If the short links can be depended upong to be permanent displaying them in a handy location on the page administration forms may be beneficial for several reasons.

Ideally a permalink would link to a given page even if a user attempted to sabotage himself by changing the slug.