Wasn't a fan of the storyline for BR 2049 so here's my alternative version.
The teaser trailer is part of the first act of the film. K finds out where Deckard is living and persuades him to come out of retirement and return to the Blade Runner department. K tells Deckard there have been a number of deaths committed by next gen replicants. Next gen replicants have a new fail safe command that limits complete free will and prevents them going rogue but it's believed their code has been hacked and subverted. The dept has been tracking prominent next gen replicants and has a list of the most dangerous. K and Deckard are hired to retire the three most dangerous replicants.
Deckard tells K that Rachel died years ago. Although she was a replicant he gave her a human funeral burial. K tells Deckard that his girlfriend was killed by a rogue replicant and that's why he joined the Blade Runner dept.
As the story progresses it is revealed that K's girlfriend's death ties into a greater conspiracy involving a secret tier of government within government: the neo-state. The neo-state are corrupt politicians and industrialists whom have teamed up with an evil group of next gen replicants (three of them are on Deckard and K's hit list). The neo-state and the evil gang of next gen replicants control Los Angeles crime rackets. They're also illegally selling weapons to off-planet colonies. Can Deckard and K stop this conspiracy or will LA be forever under the control of the neo-state and the evil next gen replicants?!
The potential advantage of this storyline is :
Deckard is introduced earlier on in act one.
The plot is sci-fi noir. We see Deckard and his younger assistant investigating the case, following up the leads. It's a mystery that needs to be uncovered.
K's girlfriend was killed by a rogue replicant and this gives K's purpose in the story more weight. He has a vested interest in stopping the next gen replicants.
During their investigation, a next gen gang member replicant - named Odessa - turns informer. She is given immunity from prosecution if she helps LA PD and the Blade Runner dept. Deckard is unconvinced she is genuine, she could be playing both sides against each other. This subplot develops with Odessa trying to exploit Deckard's loneliness. She senses his loss over Rachel and tries to comfort him. This gives Deckard a bit of an emotional crisis. Should he allow Odessa to comfort him or should he remain cold? Is she genuine or playing with his emotions? Can any next gen replicant be trusted?
Los Angeles itself is under threat. The scale of the movie is bigger than the original Blade Runner. It's not just about Deckard and K retiring three rogue replicants, it's about a bigger conspiracy. This ups the stakes.
I think this would be faithful to the spirit of the original movie and expand the Blade Runner world. Deckard would still play a major role in the storyline but his assistant - K - would share equal screen time. Deckard would remain a human. There would be no suggestion Deckard is a replicant.
The final scene of the movie sees Deckard saying to K: "Replicants are just as flawed as humans. The only difference is humans see their flaws, replicants don't. That's why they'll always be weaker than us."
Deckard's comments sum up the theme of the movie. No matter how advanced the replicant, no matter how advanced the technology, it can never replace humanity.