I am afraid that Hogosha deals artifacts for Corsairs, not OSC. Hogosha is far more important for Corsairs than OSC would ever be in this regard, they'd happily ditch you once they can to split your share between them like it happened with the GMG.
And all your wealthy clients onboard your liners are just prime targets for Corsairs once you stop being useful.
Oh, I don't think that. With how Xenophobic the Hogosha is they would Ruin it with the Corsairs. It has a reason why they use us as the Middleman. Also, I am sure that the Junkers would be more than happy to take over the Trade. or Maybe one of the Rheinland Factions like the Bundschu? or the LBW? there are Dozens of Options to Replace the Hogosha in RP.
Also you forget one IMPORTANT thing. The Wealthy Clients you talk about that could be target by the Corsairs are exactly the CUSTOMERS THAT BUY THE ARTIFACTS.