While I mentioned DVDShrink as an option if the final disc is oversized because for small percentages it's just faster (but it wasn't strongly recommended).

If you are going to go to the trouble of re-encoding, it makes more sense to do it from your scripts re-encoding the source PAL.

DVDShrink doesn't re-encode video, it compresses it by finding and dropping data where it can. DVD Rebuilder would push the entire DVD, movie and extras, through a second re-encoding. I would be more worried about how that would look.