Firstly this is a good idea. Athough, people may abuse this and keep buying unbans there could potentially be a limit in which players can only buy one unban and then if they re-offend they would be perm banned. Also, since players are able to just buy a new accound or use an alt , this happens almost everyday with the vast majority of the hackers. I beleive that legit players that may have had a one off encounter with a hacked client that genuinely want a second chance would be able to simply buy an unban and carry on playing on the server knowing that they are on their last warning. Furthermore , this would also generate quite a large amount of money towards the server allowing the purchase of new security systems or a better host to try to reduce lag issues.