Hi guys, I don't even have the game yet (live in Canada), but I thought I'd jump in anyway. Please correct me if any of my assumptions are wrong.

1) The frequency and size of the pirate attacks should be based realistically on economic conditions. Pirates are about pillaging - no loot, no attack. So if the player is slow building up, the pirates should demand less money, attack less and in smaller numbers (i.e. no "slider" necessary).
2) Pirates should attack for maximum gain with minimum effort (i.e. survival instinct). They should act like parasites effectively.
3) Pirates don't schedule their attacks - they should be somewhat random. Generally, they should attack when they're not too drunk.
4) Bribing pirates is done so they don't attack you, *not* so that they will attack the enemy. They're pirates, not mercenaries.
5) Even when you do pay off pirates, they might still attack you (too drunk to remember), the enemy (sober), both (too drunk to care), or no one (too drunk).
In other words, if pirates are integral to the game, make them *act* like pirates.
Cheers!