Just a though on the pipe's if you aren't a good welder.....Use a grinder and a flap wheel, smooth them out and you won't be able to tell.
I really think coating would be a good idea. They'll corrode if not
Yeah unless you can coat the insides with like a high pressure powdercoat I don't see why you'd want them out of something that will for sure rust. Not by any means knocking you I just don't really get it?