Probably more trouble than it's worth. I think I'll wait for Diplomacy. I'm probably going to upgrade my mod to Diplomacy anyway. I was already having problems with the current Entrenchment diplomatic features. Upgrading my mod seems less of a bother than trying to make the current system work.
You could try giving their base the artifact that allows wormhole travel on a particular map. Test it by only connecting the pirate base to a wormhole, and then have the other wormhole connect to the homeworlds. If you get a pirate raid to attack you, you'll know if it works.