Whether let Zoners have enemies or not, still doesn't matter, after so many years, Zoners should have sufficient technology and cash to build and maintain those huge ships and residing on deeper space, where they happen to meet "the antagonist" of this game just approx 2 holes away, they should have created a fleet by now, for just in case, someone poses a danger to their home.
And Zoners cannot depend on anyone particular to help them all the time against an attack. About the point, how can they make available such equipments to build a fleet - I must say, Zoners as in particular have the most reliable relation with most houses, so, getting those goods shouldn't be a problem.
As per all the House Spaces, they already have strict laws about not letting those capitals enter their zone. So, basically anyone trying to troll with that will end up getting boomed or escorted back. Just few have the permission in some house spaces, due to their specific RP, that asks them to have one.