I think the "Bad Choice Road" motif is going to be synonymous w/ BCS in the same way "No more half measures" is for BB.

I couldn't help but think about it during the opening scene in the finale with Jimmy and Mike. In my head canon, it was actually Jimmy's prompt in asking Mike about the time machine that made him develop this philosophy about the "BCR" in the first place.

First, Mike responds with a date in 2001, presumably something to do with his son. Then, his eyes light up and he becomes uncharacteristically animated for a second, and he changes his mind. "No, let me take that back...." and proceeds to mention a day in the 1980's when he took his first bribe. I think the act of tracing back his bad decisions in that moment, and landing on the day of that first bribe, get his wheels spinning about the paths you can take in life, and where that first misstep may have been.

Then, a few weeks later from that conversation, we get the car scene from Season 5 in the aftermath of the Bagman events where Mike shares his Bad Choice Road idea to Jimmy. I wonder if his philosophy would have been as solid in that moment if Jimmy's questions about regret didn't put the gears in motion.

To extrapolate on that theme, you could view the entirety of the show we've been watching since episode 1, as essentially, "Jimmy's Bad Choice Road". If Jimmy could go back in time, where would he have went? Well, I think the flashback at the end with Chuck gives us the answer and is framed as such in the episode. That flashback is mere days before the pilot of BCS, possibly even the day before. Jimmy and Chuck bickering over Jimmy not bringing "The Financial Times" in the finale flashback is a direct callback to their first scene together in the pilot, where Chuck mentions how he is happy Jimmy brought it this time. As Jimmy said when he was testifying, "I should have tried harder". This scene shows Chuck reaching out to Jimmy and trying to connect, which Jimmy denies and then shrinks back into their same tense dynamic that has been plaguing them since childhood. He felt obligated to take care of his brother, but the idea of casually enjoying each other's company was foreign to him. This is the day Jimmy would go back to with that time machine, and he would have stayed there with Chuck and told him stories about public masturbators and teenage shoplifting until the sun came up, if he had another chance. Maybe it would have made things turn out differently.

But then, there wouldn't be a Better Call Saul if that were the case, since we the audience would arrive the very next day after that flashback, where the journey will begin as destiny would have it.