Hi there

Couple of things

The Geisha are Kunoichi - This was a decision where we felt that more folks could i.d the Geisha name than Kunoichi.
Metsuke - We felt that we didn't want people getting confused with Ninja which were also refered to as Shinobi.

These decisions can be argued and debated for a long time. I know we certainly did.

As for cannons in the Single player game they are a benefit of trading with the Nanban. You might get them if you invest enough in learning how to build them yourself.

Intrepid