This is kind of a stretch, but mabye.
You could give us all resevered slots. I know how to set it up on the client side but not on the server side. What I was thinking, is having one slot on the server that is reserved, and then 16 public slots, so 17 in total. And then when an ATOT person logs in it boots the highest ping or lowest score or something. The serrver will reconinse that its an ATOT person because we will run the autoexec.cfg file that has some special password in it. Again, I dont know how to set this up on the server side. But this way anyone from AT has a spot garented. So if you make it public, AT players will still have top priority.