So this is a double suggestion, but if it's within possibility, users should have the ability the delete their own accounts as they please instead of making a post and taking either Admin or Prephil.

Second suggestion would be a splash screen/page for new members that gives them a mini tour of the site. That way, you don't have newbies posting request posts in the wrong thread since that's becoming more and more common.

On your first suggestion, this is a great idea. It should be as something as showing a notification (leading to an outline) for new registrations.

As for account deletions, these need to be done manually for a few reasons. First, when an account is deleted, the posts are not. This needs to be done on our end if it's requested. Second, it's often necessary to rename the account -- one of the most common reasons people request deletion is because they've reused a username from elsewhere and it shows in Google search results. Unless we change the username manually, the old name remains attached to old posts. As mentioned, posts are not deleted automatically. When a request comes in, we find out which posts, if any, need to be removed and whether the username needs to be switched. Once an account is deleted, the posts are orphaned and it's almost impossible to remove them.

Another reason we don't let users delete accounts without our assistance is because we have a huge problem with trolls and spammers. When someone signs up and spams the board -- models do this often -- we retain the account to guard against future registration attempts and to log what actually happened.