As in, no gravity wells that access the system. No sun, no gas giants, no jump points, only nascent gravity wells. Maybe only one or two of these, maybe as quest locations, but I think it would be neat to have such systems. Colonies on planets in these systems would probably be unable to access the global market, so would make minimal money and have minimal accessibility, but they would never be threatened by other factions.
To go along with this, a new utility ship that allows captains to use Transverse Jump without having a very particular set of skills, allowing them access to these systems and making the Navigation skill less incredibly valuable.