Yet you considered in another thread (Galaxy populator) a client-server model
Though note I didn't say it was a good
idea... At any rate, networking code controlled by the core game has rather more manageable security implications than that controlled by OXPs.
Use case: lets have a symmetric galaxy map (2 axes of symmetry to allow up to 4 players).
Okay, here's a way you could do something like that - with a current nightly build, no more! - assuming as with any open source network game you trusted people not to cheat too much.
1) Create an OXZ that allows the player to pick a faction and contains the current allocation of systems to the factions, adding NPC faction ships as appropriate, with relevant responses to the player.
2) Playing the OXZ will offer missions for the factions which adjust the balance of control in particular systems (which could, in the first version, simply be "dock at this station"). Perhaps you might require the missions to be carried out in a particular ship for fairness, perhaps you might just assess the power level of the player's ship and balance the missions accordingly. You can set conflicts with particular OXPs you'd rather people didn't use at all, though that's only a convenience measure for honest players, not a security feature. Completing a mission generates a particular string of characters.
3) The player copies and pastes the character string into a web page on the server. This notifies the server that the mission is complete. Faction control is adjusted accordingly. The web page prints a different string which the player types into a mission screen to receive their mission reward in-game.
4) Periodically (daily? weekly?), the server builds a new version of the OXZ with an incremented version number and the latest faction data. Players must be running the latest version for their mission success codes to be accepted by the server, but with the OXZ manager that's easy to get (you might want to split the OXZ into two: one small regularly-updated part that just stores current faction control data, and one large part with the graphical assets and the rest of the scripting that is updated less often, to save download time).