I don't have enough reputation to put this as a comment, so I'll just leave it here: one way that a sound change can occur between two PoA without ever moving through all of the intermediate positions is through secondary articulations that gradually become more prominent, while the original primary articulation is lenited or lost. This is in fact present in your example of "labiovelar stop to labial", and is also the reason for phenomena like r-labialization (many english varieties have actual phonetic labialization of /r/, without losing the rhotic articulation.) While these sort of changes appear to "jump" from one articulation to another, the process can still be a gradual one, since both articulations can be present at the same time.
Besides labialization, some other secondary articulations that can become primary are palatalization and glottalization.
Changes like debuccalization are probably a true example of "skipping" discontinuously from one articulation to another.
Another example would be the change t > k commonly seem in Polynesian languages, which seems to occur without passing through all the "intermediate" articulations that are physically between them in the mouth.