I'm considering beginning a program that functions as a community-based 'ban' list.

It's for an online game, where users host their own servers. These servers use a .txt file to store the usernames of who has been banned from the server. There are hundreds of different game servers and hosts, so I need to get it so that with the consent of the server administrators, these .txt files are sent to a server in which their contents are all merged. From there, I need it to automatically go through the list and remove any name that hasn't been banned for x reason(s). Then, it needs to compile the remaining names back into a single .txt file, which is then sent back to all servers, updating the .txt they already have with the latest version. What is the best way to do this?