I don't think they've ever actually said or shown you can control a ship's cannons directly. I believe that may only be a land cannon / Gatling gun feature. It's quite possible this is true of cannon emplacements and towers as well since they haven't shown or talked about controlling those either.
I'd love to be able to control all the ranged weapons in 3rd person like this, but I doubt that's possible. I think only the ground artillery units will have the 3rd person control feature.