Should I redo my bathroom plumbing?

cross-posted from: https://sh.itjust.works/post/59403600

Hey all! This is a bit of a follow-up to a post I made a couple months ago regarding our bathroom reno: https://sh.itjust.works/post/56769265

Long story short, the mortar bed subfloor was crumbling away, and I could literally tear up chunks with my bear hands, so we decided to take it all out. I'm going to sister all the joists to re-level the floor, put in blocking for under the clawfoot tub, then 3/4" plywood subfloor, Ditra, and tile. But that's not what this post is about.

This post is about all that copper plumbing. I think the stuff above the tub spout is relatively new, but I think everything below that (tub supplies, toilet supply, sink supplies) is a lot older, maybe original, which would make that close to 70 years old. Some of it looks pretty crusty and corroded to my untrained eye, so my question is, should I redo any of that copper while I've got the wall open? If so, to what extent, and with copper or PEX? I mentioned earlier that we're putting in a clawfoot tub, so we won't need basically anything above the tub spout. I know clawfoots traditionally have supplies coming up through the floor, so I may end up reconfiguring to accommodate that, but I'm also considering taking the easy way out there and using some flex hose coming out of the wall.

I don't have a torch or a PEX crimping tool, so either way I go I'm gonna have to buy a new toy. But which one? How would y'all go about this? Thanks in advance for the input!