From the game play point of view, you would need to find the balance between coastal defence, and open water convoy defence. Cut one too thin and the opponent would make you bleed there. (And if you're on the offence, put too little pressure on one, and they'll pull resources from the other and crush you.)
This is exactly what im aiming for....all about the player balancing what forces they have at their disposal. and designating the important regions and objectives to focus there defense on.