I think the drain 1/8 bend is Brass Joe. The corrosion is probably from the escutcheons. I think he could just unsweat those valves, remove the escutcheons, clean up the pipes and put new escutcheons and soldered 1/4 turn supply valves on there. No need to cut wall IMO. Well, that's what I would do. I would also check the drain stub out, and switch out the trap, of course.
Gerard, if I was you, I would replace all of your supplies that look like this. They have really had it. Probably original.
" A lot of men build things, and a lot of things fall down "