I like Edward Teach for a Leader choice but definitely not Pirate Republic.
They are adding Pirate mechanics to the game, which is interesting, and good, but why do we need one Civilization that is only pirating and not a real Civilization? Sounds counterintuitive.
Now here is what I think. They want to make the middle of the game more interesting. Then the Pirate Republic and Pirates in general should "replace" Barbarians as a midgame threat, sort of like Creeps in Warcraft.
Declaring war on everyone, plundering and causing a bit of chaos, but also being a diplomatic character that you could reason with and buy out to attack your enemies.
Just giving the player an option to be the pirates feels a bit like selling out. It's like risk adverse. Why not try something a bit strange? Maybe because they've been getting so much backlash on new and strange mechanics.
Well, I think Pirates as a Civilization strikes me as more strange than if they were a chaotic mid-game mechanic.