Is it acceptable to use multiple PVC couplings when routing a drain through joists?
Coupling a drain through the joists are even done in new work, sometimes it is the only way.

Cast iron and especially any galvanized pipe connected to it will sure rust through over the ages. If you have any galvanized pipe in place and you yank on it a bit, you may find it readily cracks loose or separates at the joints. If the cast iron is in good shape, many times the shaking of the pipes during renovation will cause the leaded joints to leak.