By no means it should be a main unit.
I understand what you are saying.
I also prefer the navy/gunpowder focus, but please, no organ guns!
If you check a thread I made on AoE3 about Portugal Historical Referencing, I have a few books that I recommend and a few free pdf aswell with a lot of great information.
Unfortunately it focus a bit more 15th to 17th century as it is my preferred area of study.