In a utopian MD with more activity, perhaps the chained quests concept could fit nicely with this; imagine tiered quests, starting with one a newb could complete that rewards land-specific resources, leads to a more complicated quest that requires or suggests you to pay a toll to access a certain place the price of which is a resource gained by the first quest, leads to a more complicated quest that could end in citizenship?
Also - perhaps as a player gains more cartography, tolls lower naturally? Or maybe volition? I'm not sure...maybe even land loyalty, though presumably citizens get through free, I dunno. But that could help prevent full closure of any location.
Dang it, foiled again! Good thing I didn't put 100%! I almost did