I actually might...have that? I 'unno. I know I'm approaching this from the same angle Bryke would've, i.e. building for a one-season story because I don't know if the show'll be picked up for more. So it'd be important that all the characters have some form of acceptable closure. That being said, I of all the characters that I'd be 'okay' with leaving unresolved, Mako'd be the top pick. Not 'unresolved' but more unredeemed...or more accurately, 'still wrestling with shit'. Character Sequel Bait.
...
Zuko. He'd be Zuko. Okay, so Korra...

Oh buzz off I'm a busy man! Anyway:
So in the original Book Air, Korra's arc was...very muddled. Yes, the plot was a structural garbage and that didn't help, but mostly it was that the show was
telling us she couldn't punch her way to victory, then proceeded to show her
punching her way to victory. That being said, I think there's foundation there that can be used, which is that she doesn't understand who she
is and I mean that in a very literal sense.
My version of Korra would largely remain intact from what was in the show (not the least of which because J Varney was a cornerstone in making that show bearable), but the
motivation for that behavior would be far more clear and present. Essentially, my story of Korra would Identity Crisis: The Animated Series.
We'd have this character who has grown up being conditioned with expectations born from OWL's assumptions about what the Avatar is and as a result of being shut away from the outside world and being only exposed to this viewpoint, she wouldn't understand her own identity as Korra. She understand on the conscious level that she's a human being born from a mother and father, and given a name as a form of identification, but she identifies as the
title 'Avatar' rather than as the
person Korra. 'nother words, she's under the belief that every aspect of who she
is, is exclusively the result of her being the Avatar. She is the way she is, because that's what the Avatar is supposed to be.
Her story would be about how this assumption gets ripped apart upon being put into practice in Republic City, and how she learns to separate her identity from a title and essentially realize her own person hood. So she'd still be headstrong, impulsive and try to punch her way to victory, but now it would be because she thinks that's what The Avatar is supposed to do. She'd still have this spiritual block that keeps her from airbending, because she has yet to realize who she truly is. The content's the same, just the context is different...except the
challenges she faces would be different, or at least framed differently. I'd already establish her as powerful and unbeatable in a fight, but make it'd a point to show that winning physical scuffles she gets into
doesn't solve her problems, they just create more fights. So what does she need to do?
Talk. She needs to talk.
Her story and her growth would largely be social in nature. How she develops her relationships with other people in Republic City would be how her story is told and since idendity is the core theme at play, it'd be the lens through which those people interact with her. Their interactions and responses would be the avenue for her character arc, as most of them would first view her as 'The Avatar' like she does thus reinforcing this unhealthy viewpoint and then learning who she truly is as a person and either challenging or developing her growth as a result, with the inevitable goal being that she learns who she is as Korra is what makes her the Avatar, not the other way around.
So who is Korra?
Korra is someone who empathetic, selfless and determined. She has an innate and deeply held resolve to help people and while she has difficulty understanding 'the larger picture' and making long-term decisions on that scale, her honesty and vulnerability make her approachable on a personal level and that's where her strength lies. Her success in the story would not be in beating up the bad guys and saving the day, but in helping the people around her realize their full potential to aid in helping the city save itself. She doesn't defeat Amon/Tarlok, her interactions with Tenzin allow him to overcome his hesitant nature and fight for what he feels is right. She doesn't defeat Sato, Asami gains the courage and will to choose a path for herself as a result of her relationship with Korra. And so on.
Like, I'd have this side-plot where she'd learn that Aang considered Avatar Kuruk to be one of the best Avatars in all history because he actually did his job of
keeping balance rather than having to
restore it, and not through massive feats of bending prowess. He was just a really personable guy who knew how to talk to people. He was a great Avatar because he stopped the fights before they happened.
Plot-wise, Korra's final 'battle' would be talking down Noatak after he kidnaps Tarlok intending to off/de-bend them both in some back alley that no-one bears witness to. Her journey would be a personal one and her actualization would be using powers that are entirely Korra's in origin, rather than the Avatars.
So yeah...I'd turn her story into a Visual Novel. Sue me.