We use NBR for gaskets, laser cuts them quick, and there is no galvanic issue, as there is no contact at area.
You can try to make housing all out of plastic, there is a good engineering reason why we do not.
Sorry, I'm sure you can figure out that we would have used it if possible.
If metal fittings are a issue, we could just make the housing with AL bards instead of NPF threads. Our industrial units have this, no big deal since our CNC lathe can spit out 100's a day
I'm not sure the corrosion issue is that big guys, hasn't been for us in the past, good anodizing really does work.