I somewhat agree though I guess I shouldn't be allowed to say much on the matter. What I feel like would be the best is a type of strike or point system.
Based on the offense that the user has caused will give the player a number of points, for example, if the user was banned on a gmod server such as TTT for a specific type of thing such as RDM for let's say like intentionally RDM and other things such as toxicity then the player would get an accumulation of points which could have been added to other points if he had any from a different server on GFL.
Based on the number of points that the user received in that category would alone ban them from the server, game type or all servers.
What would also make a difference is if those points expired depending on what type of points were added; this would also make it very easy for staff to keep track of user's points along with how close a player is to getting perm banned. Which later, could expire based on what type of points and/or ban was given to the user.
Example if an admin gave the user warning points, and later came back and another admin gave him points on a different game server for almost the same identical thing then maybe the user should be temporarily banned from all game servers for a set amount until the points expire which could tie into how perm bans and stuff like getting banned from hacking would affect the user.
To add even more even if those points expired to have them still on the user's account, so if he does come back but does something that warrants a very special type of points or accumulations of points then to ban or increase the user's ban length even longer.
This in return would still allow players to come back without having to do a type of appeal but would still restrict and make players learn about their actions even more. If the player wanted to instead he could appeal or challenge those points which for example could make his ban time less or so .etc, kinda like a prison or jail system, I guess...