Any countermessure you plan to implement, gathering fatigue, levelling fatigue, item exclusivity etc, will only harm the honest players.
Anything is hackable and RMTable. Any countermessure will get its counter-countermessure from the same RMTs. And in the end it will only be a pain for the players.
Just plain ban them and sorted. Same as botting afk players. No answer to a tell? Sorry mate, you were supposed to be there when you were moving around.
It's so obvious I don't even understand what kind of investigation is needed to prove all this.