to Ben,
Those are interesting arguments (which I have read before), but they do not negate the arguments for Luke 3.1-2 having formed the beginning of a/the gospel text. The stronger I feel your arguments about Philippi are, the more I want to integrate them into what I feel is the more certain contingency: that the gospel once began at 3.1-2.
It is an opinion. For "Luke", trying to make her account appears as a truthful orderly historical narration, a preface was absolutely necessary.
I do not really buy this as a guarantee for the absolute truthfulness of the account; the author positions himself (he uses a masculine participle to refer to himself, not a feminine one, so I am doing the same) as having more knowledge and even access to knowledge about such affairs than Theophilus (whoever that may be); the likelihood of Theophilus following up and finding lies seems remote; only if we knew in advance that Theophilus was at least a bit antagonistic would we be able to draw such conclusions from the preface.
What do you expect? That the author declared she is a woman?
I have a theory about that Theophilus. It had to be understood as a code name but I think the author launched the idea Theophilus was Gallio. The premise was that Gallio, during the aborted trial in Corinth, with Jews against Paul, would have heard about Jesus. Later, rather intrigued by that (deceased) man, Gallio would have wanted to know more about that Jesus. Eventually, "Luke", posing as an impartial chroniquer, would have issue his account.
Of course, the gospel is not an impartial account, and Gallio would have quickly notice that. But the audience targeted by that gospel was likely to buy the notions in the preface. And of course, the gospel was never addressed to Gallio or any other excellency.
According to Wikipedia, Gallio died around 65 AD. How convenient! That would imply the gospel was written in 65 AD at the latest!
As for ACTS, the story about Paul is told after, allegedly, two years in Rome and then stop abrutly. According to the time markers in Acts, that would put the account in Acts ending around 63 AD.
All this theory about Theophilus appears nowhere on my website because of lack of evidence.
Cordially, Bernard