I was thinking about this problem today, i think that i have found a solution. I will have to create the code for it this days and test it out.
In fact, the following would happen
When the player joins the server he will be auto SS-ed, this is already working on the SD server, if he have a black screenshot the server will auto kick him and add him to the blacklisted players.
Next time when he joins the server we will create again the screenshot and if he still have an black SS he will be permanently banned by the server script.