replacing the steel bearings with porcelin might work would cost about 3x as much what do you guys think

I mean ceramic bearings instead of metal that will rust in salt

Yea, if you could flush them good that could work. The problems I have always had running in salt is most bearings are "sealed" which to me means that salt will get in and you can't get it out.
Even if they didn't rust you would still need to get the salt crud out. My 2 cents