If plaaying as pirates which i often do or i will fly the jolly roger if playing as another nation, i use the following rules.
1. I never purchase a ship, i play with realistic ship purchase on which removes all the big ships and often you only see ships like Cutter, Lugger, Schooner etc for sale in the shipyard but i will never buy a ship.
2. I never purchase cannons, i will upgrade the ship calibure at Bermuda but i will not buy any cannons no matter how much i have sitting in my pockets.
3. I never sell ship, its far too easy to make money as it is, selling ships is one such way that makes you a millionaire fast. This is why i don't do it and the other reason, i can't find any infpormation on pirates ever selloing ships they have captured.
4. I never sell cannons, till we can find the sell multiplier this is a big problem where alot of money can be made (depending on the calibure of course) but its a way i don't like to make money. Just like the ships i can't find any kind of reference to pirates stripping the ships of cannons to sell.
5. I only replace the calibure of guns mounted onboard my ship with ones i find on a ship i have captured, opnce the guns are stripped and onboard my ship i will take what ever else i want and then sink the captured ship.
So thats my house rules when playing, nothing big just extends the fun buy not making money fast and makes it a little more realistic, if there was a way of reducing which shipyards could buy which ship types by the size of the shipyards its self that would have more realistic effecyts on the game. A small shipyard or small town (if the shipyard doesn't have different sizes) making only small ships like Sloop's etc, medium shipyards making ships up to Corvette's and Frigates and large shipyards making Galleon's, the larger Frigates, MOW's etc. While for realistic ship purchase it would be small shipyards = small ships up to Schooner's, medium shipyards = all ships up to Caravel's and large shipyrads = all ships available to buy with realistic ship purchase enabled. Right now though thats not possible since it would require an experienced coder and i have no doubt a hell of alot of work. Reducing the sell price for cannons and ships is a must but as of yet we have not been able to locate anything that adjusts the sell price for them.