We have a bathtub that has a drum trap - which appears to be lead, as do
the connecting pipes. (The stack is cast iron.) The trap is leaking.

I'm thinking to cut the lead pipe on the stack side of the trap, use a
rubber coupling to join that end to PVC from there to the tub. Is there
reason NOT to do this? The alternative would be to unsolder the lead
pipe from the stack Y, and connect the PVC there. This looks like it
would take big heat, and might never get clean enough for the new joint
to seal well.

TIA,
George