Currently, the same sitenotice message is shown for both public and private wikis. It would be great if there was a different sitenotice for private wikis. Additionally, it says, "If there is activity on this wiki you can go to Special:ManageWiki and uncheck "inactive" yourself." This does not really make sense since you must be a bureaucrat or be in any other user group which has ManageWiki permissions to be able to do this. This should be changed, too.
The mw-config repository says that contributions are welcome so I will make a pull request for this, if you are okay with that.