While trying to do some testing with this plug-in, I found a minor issue.
Let's say I want to delete someone that's a Super Admin on all of my networks. First, I have to edit their profile to demote them from having Super Admin status. Then, I go ahead and delete the user. However, neither demoting nor deleting the user updates the "site_admins" meta information across the rest of the networks. Therefore, if that user account is created again, that user automatically becomes Super Admin on all of the other networks.
Therefore, in order to delete a Super Admin from the whole system, you have to go into each individual network and demote that user before deleting them.
It would be nice if the "site_admins" meta information was checked and updated somehow when deleting a user.