Unselie hit the nail on the head. Zone 21 should not be part of a major smuggling route.
It should not even be connecting to any system but that single JH in New York. It should be a dead end system acting as the LSF Guard system, populated with LSF Guard and Liberty Navy Guard patrols.
Listen to the SP Campaign. King, a low ranking LPI, asks Juni what she knows about Alaska. Juni is a Commander in the LSF, a mid ranking officer, and all she knows is that there is a jumpgate in the heart of the Zone 21 minefield leading to a system called Alaska.
Zone 21 is heavily based upon the real life military installation of Groom Lake Air Force Base, commonly known as Area 51. Even normal military air traffic cannot pass over it without discipline. In my opinion, no LPI should be in there, and not even the Navy or LSF should be there unless High Command gave them permission to be there. It would be a small, elite group of pilots assigned to guard it.
Zone 21's security should be many times higher than Virginia's. Virginia, a normal Navy base of sorts, no one ever questions why they can't go in there. Yet with an area with this description;
obviously named after one of the most restricted military sites in the world, people question why they can't get in.
You might cry "inconvenient!" when it comes to restrictions of Liberty personnel, but hey, we in High Command can grant permanent passage to our own.
I think that any ships within Zone 21's minefield section should receive 3 warnings (allied), 2 warnings (friendly), 1 warning (neutral) or no warnings to halt, and if they don't, they can be shot. If they go into the system itself, they can be shot, regardless of diplomacy, unless they are Liberty personnel, in which case, they should be escorted back and disciplined appropriately.
As for Corsairs.. Dab also hit the nail on the head. If you have no NPCs and your allies have no NPCs there, unless you are the Angels, LSF, Phantoms or Coalition, you shouldn't be there outside of an RP event. Corsairs could conceivably be given an exception due to smuggling, but beyond that, they have no interest in taking down Liberty, who is, so to speak, the enemy of their sworn enemy.