That's just a quick thought worth sharing, probably inspired by political tweets quoting the magnificat recently. But while I'm on the subject... here are two other reasons the theory of Acts as defense of Paul has always made sense to me:
1) Luke-Acts names Augustus, Tiberius, and Claudius, but says "Caesar" when Paul appeals to Nero. If the work was pseudonymous, framed as if happening in the days of Nero, that's an amazing level of careful attention to detail.
2) Luke's Gospel goes easier on the Herodian dynasty than Mark or Matthew, including nothing negative about Herod the Great in his infancy narrative, omitting the collusion between herodians and pharisees, barely mentioning the famous sins of Antipas, and playing up Antipas' diplomacy with Pilate. In Acts, Luke only breifly maligns Agrippa I (the "King Herod" of Acts 12, who was replaced by Roman Procurators after his infamous death), and presents Agrippa II as noble and compassionate towards Paul in Caesarea. Again, as rhetorical strategy, it makes sense to put as much positive light (as possible) on Agrippa's relations since Agrippa's opinion was that Paul should go free.
These are just observations, with wisps of possible arguments. Somebody should steal this idea and work it up into genuine research. The wisdom of Luke's Jesus (and company) was foolishness to the administration of Nero, and designed to make Paul seem laughably non-threatening.
He has brought down rulers from their thrones but has lifted up the humble.
He has filled the hungry with good things but has sent the rich away empty.
Amen, Mary. And He will again.