Another thing. If you can embark only on a harbour... this mean an army who land on a enemy region/realm will be 'trapped'! If they can't take a city or a town region they will never be able to 'come back home'?
Good point. Unless you allow for ships (were we talking about implementing ships that one can purchase?) to allow friendly troops to board, therefore allowing for nobles to go pick up stranded allies.
I feel that sea zones go hand in hand with the implentation of fleets, in addition to ports. Investing in a fleet would help one's navy as investing in siege engines would help one with sieges.
