As it currently is, the “expedition” system seems to have lost everything that made the original navigation system fun in the first place so heres my idea.
Instead of having a set list of “expeditions” to complete, in order to unlock new landing sites and progress, you must first venture there on foot (or steamroller) to discover or “survey” the site, allowing you to then surface there with your drillship. Then, to progress, you must complete a specific task or objective at the location to eliminate COG presence in the immediate surrounding area
said task could be a standard “kill everything” mission, or you could destroy a nearby control tower, or eliminate a COG officer, or destroy a supply depot, etc
after clearing the area, your reward could either be the loot dropped by the COGs, or a cache full of resources or experimental schematics that they were guarding, etc
so instead of a location tied to a mission, its a mission tied to a location, and you could come back to finish any of them any time, and outside of main progression quests, they can be started and completed at any time, but they can only be completed once (bc then that location would be cleared of COGs)
think of it like conquering settlements in an open-world game, like Just Cause or Ghost of Tsushima, but where each “settlement” is a drillship landing site
it would also be satisfying watching each location slowly be checked off one by one as you take the island back from the COGs