It would make sense for a Messiah-nic abridgement of the oratorio to drop most of the second act. IIRC there's a long exchange between shepherds and angels, the landmark-of-relevancy chorus "Lift Up Your Heads, O Ye Gates" and a few other, kind of half-baked things. Whenever I listen to the Messiah I'm struck by how late the "Hallelujah" chorus is in the work. It's like how late Christmas is in the year: whenever you see a reference to Christmas anywhere, there was only a week left in that year. Basically the whole third act is golden.