>>/983293/
From memory there is already a board feature for each BO to restrict TOR posters and a seperate option for proxies. The implementation would be writing a script to get the data and schedule the task. The data returned is appended to the current IP list stopping proxy posters.

There is probably a VPN list generate each day by someone. So you could literally download it, compare current list and add new IPs that is scheduled to run once daily. I don't see that taking more than an hour.