Sadly with the current setup you'd have to start by stripping Trial accounts of most of their rights starting with mail until 10 and no messages until 10 either, that is of course unless this is in place already. We'd be better off if you SE were willing and or able to put in-game GM bots into the game that actually tally multiple results like reports and in game complaints and automatically send people to gm prison where they can be identified and dealt with afterwards by an actual person from tech support. Much easier to do than an anti hack system.
This is all assuming that SE themselves aren't the RMT's