With "reset the pirate-friendly world" I mean purely the changes made to the game world through the "piratefun" quest case in quests_common.c .I wouldn't necessarily go that far. If you leave the Brotherhood on good terms, they might not necessarily need to turn hostile unless you actively turn against them. They're wondering what you're going to do next. But I'd imagine that rank in the Brotherhood is measured by your piratical deeds and if you're not doing them any more while someone else is, he's the one everyone else is going to look up to and you're just a nobody now.
Of course, if you've got yourself a new LoM from one or more nations and are now attacking pirates then they won't take long to turn hostile. But that's going to happen anyway, so no need for any further action.
Basically, what we have now works well enough, apart from getting Isenbrandt Jurcksen to use the correct dialogs and to revert to his normal one if you leave Pirate service.
That changes the Pirate governor dialogs to become "REAL" governors and also changes a useless blacksmith to a useful one and can change Tortuga to be a real pirate town too.
Part of that definitely NEEDS to be undone (specifically those governor dialogs) and we may want the rest to be cancelled as well.
Please have a look at that section of code so that you know what I'm going on about.
What I am NOT suggesting is to "turn the pirates more hostile". I thought all of that already worked as we wanted, so no need making further changes to it.
Should all be possible.(I'm now thinking of my storyline in which the plot may call on you to stop being a pirate, but you may not want to turn against your former mates. You just aren't one of them any more. Of course, if you sail around under a nation's flag then pirates are going to want to attack you and if you don't want to become hostile to the Brotherhood then you have to avoid rather than fight them. I'd like for that to still be your choice.)
After all recent changes, if you are in the Brotherhood but flying a nation's flag and sink/capture Pirate ships, the pirates will STILL not immediately turn hostile.
They used to, but we decided to make them even more forgiving in that respect.