This might be a dumb idea but would it be possible to just lift the scene of Rey watching the ship liftoff in the TFA trailer/TFA and use that as Rey’s parents leaving? That way, you can have two different ships for Ochi and Reyrents.
Obviously, that would also mean you’d have to cut out the scene from TFA as well (although with the clip I’m linking, I think it’s an alternate shot anyways so it might work without having to cut anything).
The clip in question:
I think that could work, but it may not even be necessary. If we go with the angle that Rey’s parents don’t matter at all to this story, and that there’s therefore no reason to include them at all, we can just cut out any mention of Rey’s parents, and their connection to Ochi’s ship.
If we really want to distinguish between the ship seen in TFA and Ochi’s ship, we could just recolor the engines; but I really don’t think that’s necessary. The ship in TFA goes by so fast, most people probably wouldn’t even remember what it looks like by this film.