im not sure if someone already suggested this (i havent checked that far back). when you get a mission at a pirate base they are basically the same as the police missions but with different enemys. what about a mission where you go to a target trade lane, take it down, and raid a transport convoy. it seems that this is a possible mission type (maybe with cargo delivery back to base, like the capture missions).

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Attacking 1 pirate = Good
2 Pirates = ok
8 Pirates = Very Bad