We can already assign all moderator permissions to individual users or user groups via "User Group Permissions" and "User Permissions," so why is there a separate tab for "Moderators," which lets us assign these permissions with less stylish and less in-depth checkboxes? As far as I can tell, this entire "Moderators" tab could be removed and we'd still have all the existing functionality.
Admin powers are a little different. I'd like to propose that the admin powers become assignable in the standard user and group permissions areas. "Manage add-ons", "Upgrade XenForo", etc, could all be permissions which can be default / allow / deny, just like everything else. This way, the "Administrators" tab could be removed as well. Everything would be managed under user groups and user permissions.
I feel that these changes would make moderator and admin permissions a lot more standardized, and it would make sense for them to fit into the existing permission system. Also, "Moderators" and "Administrative" would no longer need to be special, undeletable groups.
This would also eliminate the need for special "Super Moderators" and "Forum Moderators," because a user group could be created with node permissions on that forum, then the user could be assigned to that group.