Another issue is that from what I can tell, the isolation is fairly enforced by the will of the players to actually make an impact on things.
If you have 'hubs' where multiple factions interact, then you have multiple FMs butting heads over various groups trying to get shit done and effecting both factions and it basically becomes a form of PvP.
And as I pointed out to you before, that's never going to fly (due to trust issues inherent in the system) as long as there's one overriding Admin who is also in control of the largest, most powerful faction. The isolation of factions, from what I can tell looking through the archives and generally judging from the history, dates back to approximately the Freespacer Genocide, where one FM's faction tried to make a significant impact on another FM's, and got their shit so thoroughly wrecked, without any chance to gainsay it from what I can tell, that the faction has effectively stopped existing except as an extension of Nepleslia.
Hubs would bring about more of these situations, which FMs and by extension, GMs running plots under the aegis of an FM, would be reluctant to get involved in, for fear of triggering a similar thing and having their brain childs obliterated because they dared to challenge the power of the Admin and largest, strongest faction in the game.
edit: For this to ever be a thing. The person in charge of administering the WHOLE SITE, and anyone put in charge of administering neutral areas, must put themselves outside of the Factional Fictional Politics of this entire situation, and how incredibly personal they get, and further, the factions, as they exist right now, have to be put on far more equal footing in some manner. Both technologically, populationally, defensively, and offensively, at least in some manner approaching a perfect imbalance where the whole thing has a form of equilibrium.
Until that's achieved, having 'neutral hubs' that were more meaningful than places for PCs to interact and shoot the shit, without having any actual plots going on for them that could possibly significantly impact the metaplot, is going to be incredibly difficult to achieve, if not completely impossible. Simply due to massive imbalances in both OOC and IC power between Factions, the people running and playing in those factions, and the history of how those imbalances have been exploited in the past (how the whole IWL and Freespacer Genocide were handled in such a one sided manner without allowing for a response by their FM), have lead to this situation.