What about an option to block search engines for all sites in the network?
Settings > Privacy > Site Visibility > Ask search engines not to index this site.
Now I have to go to every site and block it one by one. I think it should be nice to have an option to set the visibility for all, maybe even with exceptions.
And when I want to unblock them, I also have to go back and set it one by one. Time saving required, I guess :)