SP survival. I am exploring pirate territory right now. Killing Zirax, quickly gives you a great reputation among the pirates. In short, they downright adore me. Nevertheless, I can't get into most of the POIs because the wrong faction. there are so many interesting pirate objects that i can't visit. Is there even the possibility of joining a faction in the SP?
You can create and join your own faction, though it's rather pointless. Can you join an NPC faction? No, you're not an NPC. As for those interesting places you can't get into, yep, that happens. Your options are somewhat limited - you might get lucky and have an NPC open a door and you can try to slip in, but you'll find getting back out to be challenging, or you blast your way in, make an enemy and go explore. That's pretty much it for options.
OK then something is wrong with the POIs. The doors should all be set to "public". Unless they belong to a scenario or a quest Creator-Rules: "Make sure ALL doors, ramps, hangadoors, etc... are set to 0000 BUT you can of course lock off doors that should have an access restriction with a code or signal logic"