Nice mod!
Here are a couple things:
Why would I get the Pirate when I can get a Pirate Harpooner for 1 extra resource? The 1 less morale and attack doesn't really concern me. Perhaps make them a bit more expensive, or Pirates a bit cheaper? If Regular Joe Pirate had less resource-hogging armor, I could also mass them and they would have their own niche. Right now I would never use them.
Pirate Lords are... bizarre. Would it make sense for them to have a bit of priestly power as well? I usually only get two paths, but the possibility for who-knows-what is pretty exciting
Is there a reason there is no blessable unit? It seems the Redguard might be a good choice, and it would limit the number recruitable so you don't get "elites only" armies.
Wind Channelers seem kind of meh for their cost - at least in comparison to the Arcanists, who are awesome. I think I'd only recruit one if I was very low on gold. If the Arcanists were capitol-only, it would make it a much more difficult choice, though the nation would be significantly weaker.
One other thing I would add - and this might just be me - would be an Animal Trader or something that freespawned various exotic pets for the pirates.