I'm just going to brush off your buffoonery here and YES, I know what privateer means. Do you want me to list its similar counterparts as well? There's corsairs and raiders too. Think this through. In ME2, the Alliance also have their own privateers like Jacob said and even though they are supposed to hit the mercs for them, the Alliance still wants to maintain minimal contact with them in case the corsairs did something that could tarnish their image.
But giving a ruling title to a raider? I'll let you figure out the consequences. Same thing why Rivain don't bestow a title equivalent to that of a bann to your "oh-so-REAL pirate queen" Isabela.
Its not like privateers were never rewarded in real life. Sir Francis Drake was knighted by Queen Elizabeth for privateering the Spanish especially well.
That said, strictly speaking her marriage to Bryce isn't legally the same as giving her a ruling title; she isn't the ruler except insofar as her husband allows her to use the perks of his title. And unless he was responsible to a head-of-family at the time there's not much anyone can do to prevent him from doing that. (Unless Ferelden's crown can veto marriages, which seems like exactly the sort of power Ferelden wouldn't give a monarch.) Or did the WoT story state that she was made a Bann for her services and then Bryce married the newly-minted noblewoman he'd fallen in love with while she was a commoner?
(Edit: Now that I read the original post more closely, is the idea that her father being a Bann and being a raider were separate, and that her father was a legal (or, considering the occuptation, probably more "rightful") Bann who pirated on his own free time? Because I don't see why one would interfere with the other unless he was hitting Ferelden ships.)