A couple months back I put together a simple Admin-only chat prefix that does a quick permission check and shows chats prefixed with "/admin" to administrators only. There's also a small template mod to show an [Admin] tag.
Admins see this:
View attachment 38304
Non-Admins see this:
View attachment 38305
I was wondering if this could become a supported feature. I'd be happy to share the modifications with you or (with permission) anyone else who's interested.
I don't use any extra database fields, but rather check the prefix and permissions every time the chats are loaded (speed mode is disabled for security). It's not efficient but it works well for the relatively small board I've been working on.