I'm with most of vk's idea, having played it some, a lot of people really just don't seem to care about capturing (unless a mod is watching, lol). It becomes just another map for gb.. or more like gb2 with a stationary flag. But if people are into capturing though, it is a lot of fun.
My suggestion is for the objective to be "Capture enemy island OR destoy all enemy vessels."
Of course the emphasis would be on capture which will give bonuses and such. Currently I've noticed that xp seems to be somewhat proportional to one's individual attack (if not using APA), but if team wins one gets a lot of credits and points. Well it seems like an ok alternative. Like if you want sure xp play gb, but if you need a boost in credits and points, here's occupation mode for you.
Which kind of makes sense if you think about the island having resources which your team is looting or something like that. But that's another story.
Also, to further emphasize the importance of capturing the island, maybe put a penalty for shooting it. I mean, if there are resources on the island, they won't be any good if destroyed.
Moving the 4 bases and speed capture bonus, those too I like. :D