A recent post on reddit (which was promptly deleted by a mod) revealed that it is likely that hackers do no necessarily have to purchase a new copy of DayZ in order to play again following a ban from hacking. Obviously I have no idea if you are aware of this already, but it is worth mentioning in case the dev team have not yet heard of this.

Since the people that fall into this group offer zero to the community it seems like a sensible option to address some part of the hacking problem is to figure out how they are creating a new version of the game without buying a new copy. If security measures could be introduced that dealt with this, then they would either stop playing (good), or would be forced to buy another copy (also good, assuming they play legit or are promptly banned again if they cheat).

Unfortunately I do not know anything about the methodology involved, but I'm sure with some careful research it may be possible to uncover this.