I love the idea ! And it would proove a good income for licences for official factions
Use the "system base" mechanic you use with the PoBs and combine it with the "redirect to Conn" mechanic , perhaps ?
And then let the player build cargo module slots on a planet, but only cargo slots...
you would need a PW / login to acces the cargo spot, and it would be either VERY costly and very small, or would need upkeep like a PoB without the possibillity of an attack but with the possibillity of a FR5 ;-)