Hell, that's too easy to evade a ban, what can we do ?
Oh I know.
A tool in-game incorporated that detects cheats, or softs that act on paintball2.exe . That's the best way to do it, servers would launch it automatically (with an option for those who want to cheat privately) and if it detects a cheat => Life time ban (or less if you think it's too bad for poor lows that need to cheat)