Defecate in his shop. And if asked why, reply that he's coming into your workplace and shitting on your ability to make a living.
Does he leave the rank at predictable times, e.g. for lunch? Then maybe double-park a few minutes before, walk away, and block him in for 30 mins.
On a serious note, is the rank used by taxis all the time? It could be that he's been looking at an empty rank for the past few months and thought to himself, if the taxis won't use it, I will.