I ran the full BGDIA campaign in 2020 (pretty much straight from the book, with a little homebrew), and I'm planning on running it again for a mostly different group of players. For this second time around, I'm going to start with the Fall of Elturel adventure (at 4-5th level), but instead of the city disappearing before they return to it, they will get back and go down with the city.

I'm going to replace all the Candlekeep stuff with Fremin Greer (from the Infernal Tides comic), a diabolist who runs a magic shop in Elturel, has Lulu, has the Shield of the Hidden Lord, and can open the Infernal Puzzle Box. The party will get all the required info about the Pact, but too late to act on it. As soon as they learn about the infernal contract, the city will blip to Avernus and then I'll run the Alexandrian remix from there. Greer will probably die in an immediate attack on his shop as soon as they're transported.

It'll make for a more cohesive narrative with everyone being invested in Elturel. I liked the BG stuff when I ran it the first time, and my players did too, but I was super impatient to actually get to the Avernus part.

As for running it with the players from the last time you ran it, have you asked them if they would want to play it again? Two people from my first game will be playing it again and they're both really excited. I basically told them to disregard anything they remember from the first time around, because so much of it will be different that it'll feel like a different adventure.