I believe actually "falling away" in 2 Thes 2 could be both a rapture and a departure from the faith. I also believe, as in the Hebrew mind prophesy = pattern. The ultimate sense of apostasy would be nearing the second half. Because the way 2 Thes 2 tracks, to me, would be the man of lawlessness revealed "as" the one who demands worship at the midpoint. Otherwise, if the church is gone, who is the man of lawlessness being revealed to? The angels? The world won't notice. Nor would it want to. Blessings.
That's my take too- both rapture AND apostasy - as departure from the faith. No reason Paul couldn't have used a double meaning in that word. In fact if both apply that covers the entire church situation- Some who aren't apostate are raptured, while some who are apostate but saved, are raptured and the ones that are Christian in name only will be finding themselves left behind, and realizing they need to get saved or else.
The church as a whole is drifting into apostasy, which is expected from other passages that deal only with that form of the word. It is the end of the church age, the Laodicean era.
Similar to when Jesus came the first time- apostasy was so rampant that only a few shepherds, some gentile Wise Men and 2 faithful people in the Temple were aware that the Messiah had arrived. The religious leaders Herod consulted were well aware that Bethlehem was the place but they couldn't be bothered to move themselves over there to see for themselves. By the time of Palm Sunday, Jesus says that they SHOULD have known the time of their visitation- because that day was the fulfillment of Daniel's time prophecy - the very day He showed up on Palm Sunday.
Just from that pattern alone, we can expect apostasy. Like you said, Pattern is Prophecy to the Hebrew mindset.
Here's where I will differ with you though.
At that midpoint, the man of lawlessness being revealed, in the Temple- he is revealed to the Jews first and foremost. The Gentile believers who come to faith after the Rapture around the world will be aware, no doubt as this is one of the Time Stamps of the Tribulation that can be used to predict the day Christ will return.
The church is gone, the believers that remain are now primarily Jewish in nature. Not to say there won't be a lot of gentiles, but God's focus is now back on the Jews. Lee Brainard made a point a while ago, that the Temple in Jerusalem, is God's Temple, the Jews are back in there sacrificing. If it wasn't God's Temple, he could desecrate it to his heart's content, and it wouldn't matter.
But Satan and the AC want to be sure to desecrate what is God's so the Temple is their focus.
The man of lawlessness is being REVEALED TO THE JEWS! The ones who believe in Jesus, and the majority who either sit on the fence about Jesus, or who reject Him.
When Jesus predicts this in the Olivet discourse, He is speaking to the Jewish people of that day- reminding THEM to get out when they see this sign.
So the sign is to the JEWS! They will notice, and of course the gentile believers around the world because everyone who believes Jesus will be laser focused on this event as a time stamp to tell when the Trib will finish.