Noah saving HG Tanhauss's family would have been a stronger ending both in terms of theme and character development.
First of all, in the version of the show I'm picturing, it's made explicit that everyone who ceases to exist when the Knot is destroyed gets reincarnated in the Origin universe, and that Charlotte Doppler is Charlotte Tanhauss. Noah isn't Marek though. There can actually be a beat where Noah hopes that he's Marek but then he looks at him and somehow knows that he isn't, but also that he has to do this anyway.
So, from a thematic standpoint, Dark is a story about parental love. The problem is that we never get the impression that Jonas and Martha love their son. Now, this is fine if the point is that by the time Jonas and Martha become Adam and Eve the Knot has stripped away at their humanity, but I just don't buy that Eve was generally motivated to save her son (who she never even names!). If there's ever any sign of affection between them, I certainly don't remember it.
Noah, on the other hand, is motivated entirely by his love for Charlotte (and also Elizabeth). He's devastated when she disappears, and is willing to commit atrocities just for a chance to be able to find her. Martha may understand intellectually that Marek's father would do anything for him, but Noah would understand exactly what the means on a fundamental level. (He'd also be sub-textually saying that line to Charlotte, which if played right could be utterly heartbreaking.)
There's also the matter of the number three as a motif in Dark. In this version, there are three principal parent-child relationships that motivate the big picture events of the story: HG Tanhauss to Marek: the one that got us all into this mess, Claudia to Regina: the one that finds the way out of this mess, and Noah to Charlotte: the one that puts the plan to get us all out of this mess into action. Have the Noah who saves the day be from the Eve timeline and there's even some nice symmetry with the three worlds in the show.
Now, the characterization standpoint. The character arcs of both Jonas and Martha are, depending on the specific version, lose their humanity and become Adam and Eve, die, or sacrifice their existence to save the world. The problem with Jonas especially is that he's already willing to be erased from existence by the end of season 2, and then Martha spends season 3 mostly being a demonstration of the Schrodinger paradox, but then ultimately coming to the same conclusion.
In this version of the story, the central arc is Noah's redemption, as his love for Charlotte goes from a selfish love to a selfless love. In the first season, he's able to kill children remorselessly, even though it causes their parents the same grief that Noah felt when Charlotte was kidnapped, all in the hopes of creating a world where he and his daughter can be together again. By the end of season 3, however, he gives up Charlotte willingly, with the knowledge that this is the only way that she can have a happy life. While there may be a Noah in the final timeline, he's still giving up the thing that matters to him the most: his relationship to the people he loves. At the same time however, the only thing that remains of Knot!Noah is his most redeeming quality, the fact that Charlotte is able to live happily.
First of all, in the version of the show I'm picturing, it's made explicit that everyone who ceases to exist when the Knot is destroyed gets reincarnated in the Origin universe, and that Charlotte Doppler is Charlotte Tanhauss. Noah isn't Marek though. There can actually be a beat where Noah hopes that he's Marek but then he looks at him and somehow knows that he isn't, but also that he has to do this anyway.
So, from a thematic standpoint, Dark is a story about parental love. The problem is that we never get the impression that Jonas and Martha love their son. Now, this is fine if the point is that by the time Jonas and Martha become Adam and Eve the Knot has stripped away at their humanity, but I just don't buy that Eve was generally motivated to save her son (who she never even names!). If there's ever any sign of affection between them, I certainly don't remember it.
Noah, on the other hand, is motivated entirely by his love for Charlotte (and also Elizabeth). He's devastated when she disappears, and is willing to commit atrocities just for a chance to be able to find her. Martha may understand intellectually that Marek's father would do anything for him, but Noah would understand exactly what the means on a fundamental level. (He'd also be sub-textually saying that line to Charlotte, which if played right could be utterly heartbreaking.)
There's also the matter of the number three as a motif in Dark. In this version, there are three principal parent-child relationships that motivate the big picture events of the story: HG Tanhauss to Marek: the one that got us all into this mess, Claudia to Regina: the one that finds the way out of this mess, and Noah to Charlotte: the one that puts the plan to get us all out of this mess into action. Have the Noah who saves the day be from the Eve timeline and there's even some nice symmetry with the three worlds in the show.
Now, the characterization standpoint. The character arcs of both Jonas and Martha are, depending on the specific version, lose their humanity and become Adam and Eve, die, or sacrifice their existence to save the world. The problem with Jonas especially is that he's already willing to be erased from existence by the end of season 2, and then Martha spends season 3 mostly being a demonstration of the Schrodinger paradox, but then ultimately coming to the same conclusion.
In this version of the story, the central arc is Noah's redemption, as his love for Charlotte goes from a selfish love to a selfless love. In the first season, he's able to kill children remorselessly, even though it causes their parents the same grief that Noah felt when Charlotte was kidnapped, all in the hopes of creating a world where he and his daughter can be together again. By the end of season 3, however, he gives up Charlotte willingly, with the knowledge that this is the only way that she can have a happy life. While there may be a Noah in the final timeline, he's still giving up the thing that matters to him the most: his relationship to the people he loves. At the same time however, the only thing that remains of Knot!Noah is his most redeeming quality, the fact that Charlotte is able to live happily.