While we're thinking up stuff that won't happen, on My EQEmu Server(TM), for ZEM I would use it as a relatively gentle tide to move players about to various zones, tweaking it every two weeks so no one gets stuck with just one zone and one set of mobs being their best choice.
And while I was at it, I would make it entirely safe for players to combat mobs of light blue and above, but as the level separation increases there is an ever-increasing chance that a booming voice would suddenly say "THE GODS ARE DISGUSTED BY YOUR DISHONORABLE COMBAT, <PLAYER>" and a single lightning bolt would insta-kill said player. If it's a second offense, maybe the gods take an equipped item also.
The trigger test only occurs on offensive action of any kind against the low level mob, so if the high level player gets trained by low green mobs, they can safely get away if needed.
Voila, only appropriate-level players can farm anything, and there are already controls on number of accounts allowed. And so, as usual, all problems vanish in My Universe(TM).