Could you take the rocket turret from the Vanguard and put it on the Retaliator?

I don't know, given the current design of it. It was originally specced that you could, but whether or not that's still the case, I don't know, because I haven't touched it in a while. But it was also designed that if you are able to transpose this to other ships, it doesn't come with its suite of ammo, so you just have what's actually on the rack, which means that you get your some 30-odd shots before this is now a used turret. So buyer beware.

Yeah, when you see the Harbinger, it's got the rockets that are on there, and then there's this whole section in the back with more rockets and a cool reloading system. It's part of itself.