I think what we need most is an established character that the patrons of the cantina already know and have had dealings with.
While we don't have an assassin, per se, we do have a bounty hunter-- but she's not familiar to us. I would say that an assassin would be great, as long as she was on friendly terms with the patrons of the cantina. Or she could be a crime broker, a prostitute, a drug dealer, etc. etc.
Perhaps your character is deep to her gills in criminal activity, but often needs able hands she can trust for things that she's not quite as adept in (repairs, piloting, gathering information, etc.).