I would say, in an RP sense, its bad RP for the corsairs to know about the route that leads through Z21...just as its bad RP for the Navy to not annihilate anything that moves inside Z21.
Economically, the Corsairs have to, and that sucks. But, it should be a rather 'really really suicidal move' type of an option....lets smuggle cocaine through area 51....you see my point?
those gates should be insanely well defended.
If we shoved all the defenses of Vesspucci, with Navy and LSF Guard tags instead of hacker, into Z21.....that would make sense.