I didn't suggest anything that "massively change" the stated plot.  I openly, and in a friendly manner not meant to be ride or insulting, challenge anyone to find where I didu

A privateer is merely a specific kind of pirate that has a home country.  Those that fly that country's flag are safe from him or her.  That's all.  Privateers are sometimes even seen as heros by their own country whose citizens blindly ignore the murders while the local military see them as vicious mercenaries.  (Often they're just jealous because they have to five the loot over to the government)

As for the magic statement, you'll note Tia Dalma never threw any fireballs or anything ridiculous.  However a witch aboard an enemy vessel would be really interesting.  Sure he or she isn't going blow up your ship with magic but being able to constantly point out which way the players went could be a challenge for the crew.