You may as well replace the supply lines if you do.

Yes, I would replace it at this point. It's easy access, it's only a few feet and you can get rid of the Fernco fitting.

So a couple of other tips: There's a notched floor joist that needs to be replaced and there's galvanized supply line that need to be replaced (corner going up).

The copper is probably fine, but needs to be routed so it doesn't need the floor joist cut through.

What is it about plumbers and bathrooms?!?! I've seen floor joists cut almost all the way through (don't need no stinkin' floor joists).

Cast iron lasts a long time, but its very heavy, and designed to be supported by other cast iron pipe or by some very sturdy strapping. Since your cast iron flange is above the new PVC pipe (which would not support its weight very well), I think it would be best to replace with PVC.

Also make sure you replace all the 2" or 1.5" galvanized drain pipes for other fixtures. The horizontal runs usually have significant corrosion inside, and the small diameter means they plug up more frequently. If you take one apart, the build-up will look like the stalactite and stalagmite pictures you saw in kids books about caves.

Bruce

Thanks guys! The galvanized pipe is actually old. They just cut the pipes and left them in place. 🤦‍♂️
The joist with the cutout also isn’t technically a joist. It looks like they were only really meant to support the toilet as they don’t actually span the length of the bathroom.
I got a quote from a plumber. I know a quality plumber is worth their weight in gold, but does $850 to replace just the cast iron with pvc sound reasonable? I was expecting 350 or so for 2 hours of work. Am I crazy? Thanks again everyone.

"...does $850 to replace just the cast iron with pvc sound reasonable?"

Yes.

I think the$850 bid is a, "I don't want to mess with this... but if I do, it's going to be really worth my while" bid.

I live in an HCL area and that is a low to normal.