It is easy to accidentally make changes on the permissions page which can cause an administrator to not be able to administer. I know because I just did it, and it required going to user 1 to fix it. Given the hundreds of check boxes on the page, it would be better if Drupal provided a way to confirm permission changes before saving the changes to the database.
Example:
Goal: Set permissions for Medium Permission User, Low Permission User, and Administrator.
Current steps:
1. Go to https://sfmta.prod.acquia-sites.com/admin/people/permissions
2. Filter to show roles Low Permission User, Medium Permission User, Administrator.
3. Display all modules.
4. Click Filter Permissions.
5. Check permissions to be used.
6. As the page is very long, accidentally click permissions that you didn't mean to click.
7. Save permissions.
8. Suddenly not be able to access /admin
New feature steps:
1. Go to https://sfmta.prod.acquia-sites.com/admin/people/permissions
2. Filter to show roles Low Permission User, Medium Permission User, Administrator.
3. Display all modules.
4. Click Filter Permissions.
5. Check permissions to be used.
6. As the page is very long, accidentally click permissions that you didn't mean to click.
7. Save permissions.
8. Get confirmation message:
You have requested the following permission changes:
Low Permission User will gain [permission 1], [permission 2]
Medium Permission User will gain [permission 1], [permission 2], [permission 3]
Administrator will gain [permission 3]
Administrator will lose Administer Permissions
[continue] [return to edit] [cancel]