Not sure what you're asking here, but yeah, need permission of the person IC for it, or some way to explain how you got the design IC, not necessarily a thread but like Kyros said, a Sith cant just grab a Republic ship. I'd recommend talking about it to them ooc and seeing if whomever controls it is amicable to some shenanigans involving it. Another thing you might want to consider if you still want to run false flag operations is if the ship is even admitted to being owned by that faction you want to implicate.
@[member="sabrina"]