Interesting. While I hadn't considered head cannoning my Tav in relation to the Origin characters, there were certainly times when I had to find justifications for keeping companion plots moving. (Lae'zel, for example: After getting attacked by a Githyanki patrol - who's stated orders are to kill us - I'm still going to take Lae'zel to the creche? And when the 'cure' at the creche nearly kills her and we immediately get attacked again, I'm still supposed to be cool with going further into the base to talk with their leader? What?)
Exactly. Dilemmas like this got me thinking of ways to make sense of Tav's purpose. Tav as a bounty hunter who decides the best way to bring Astarion to Cazador is to befriend him, lead him to Baldurs Gate and then betray him (or because you've grown fond of him you betray Cazador). A Warlock sent to discover just what the hell Raphael is up to, a Harper sent to find Jaheira and Minsc. Obviously none are as satisfying as a true custom character working with a good DM but still better than aimless Tav wondering the realms and getting caught up in the Absolute crisis by sheer chance.