Assuming that it's between ANH and TESB, Car'das would be out of it. Karrde might be involved off to the side, not getting in direct contact with Han. Booster would be in Kessel, or else he could be worked in. I might not put it past Zahn to bring back someone like Mazzic from TTT. But if Han's stealing something for the Rebellion, which is likely, I'd guess it's most likely that Han would work with Wedge and the Rogues, maybe Page. But it's all just guessing.