Neat, although we would then have to make the entire Mediterranian a coastal zone IMO.
In the end though I think Archinorf is right and we'll have to stick to events, since the devs obviously do not plan to introduce the feature into the game anytime soon (CK 3 maybe?). In the mean time I'll snoop around the forum when I get the chance and see if there are any mods out there, if no then maybe it is time to fill that niche.
Of course. Also, I realized that I made a mistake; Longboats would be able to go up rivers, not go on open seas. All sea provinces should be coastal. There's no need for the open ones, anyways, with all the land being so close.
For Merchant Galleys, I'm envisioning a system that works like raiding... but in an economically constructive manner. Basically, every County has a "Goods" bar, and Merchant Galleys can be set to "trade in" a port, slowly sapping the Goods; the Patrician who is conducting the trade pays a fee, based on the total amount, to the County owner. Galleys are then able to sell, and that saps Loot.
So, for example, there are two Counties: Aland and Bealand. Aland has 10 Goods, and Bealand has 12.00 Loot, and your fleet can transport 8.00 "units" of anything. So, it takes the following route:
Move from the Sealand Republic to Aland County
Purchase 8 units of Goods, leaving 2 units left
Move from Aland County to Bealand County
Sell 8 units of Goods, gaining 8.00 Gold, and leaving 4.00 Loot.
Move from Bealand County to Sealand Republic
Cash in 8.00 Gold
Both Wealth and Goods take time to recover (as suppliers rush to provide more goods, and consumers rush to earn more disposable income), and terrain/geographical location plays a role; provinces in India or the Near East will generally have higher Goods values in their provinces, but pay less for Goods.
As such, the player would have a strong incentive to make their purchases in the Eastern Mediterranean, and then sell at multiple Western ports before returning home (assuming they are playing as an Italian republic).
Now, where Trading Posts come in is in "protecting" your purchasing and selling interests. Posts essentially reserve a large chunk (one which increases with Trading Practices tech) of the Goods and Wealth for yourself, allowing you to trade without the stress and risk of competing against better ships.
Admirals of trading fleets' Stewardship stat, as well as special trading traits, affects factors like speed of buying/selling and the value.
I know this is a thread for naval warfare, but I just now thought of all this... I also don't mean to imply, through these mechanics, that importation is economically harmful. Don't think of the Loot bar as representing, in this situation, money that's been stolen, but money that the state can tax. It would also give importers a legitimate reason to do embargoes.