Has anyone managed to make the pirates build units or bases? I managed to give them a bunch of units and they will play like a real faction and conquer planets and attack you but they dont build anything.

They attacked one of my planets before once. I have no idea how but they did. Maybe from time to time they attack and there might be some code in there for them to build or something.

You can give them the AI to make them capable of building things but i cant figure out what to change so they actually do build stuff

Have you tried giving them buildings? As far as I know they have almost no buildings, if you copied a rebel/imperial structure and gave it to them they might build it. Then again they might not of course, but it is worth a try.

I don't know what all you've changed but the pirate units in the indigenous ground companies file are all affiliated with the empire, etc. -- you would probably have to change things like this to make them operate independently.

I finally made the suckers build some corvettes, you have to change a lot of stuff and even make them "look" like a playable race so they are red on the map instead of orange now. I'm gonna try to setup a campaign with empire vs rebels vs pirates vs rebel pirates vs empire pirates, that would probably make the campaign more exciting since there will be more than one factions fighting it out, but the only true enemies will be empire vs rebellion. It would be nice if there was a way to script custom random missions but it looks we are stuck with the ones in the game.