I didn't expect to be writing this many parts to this series.
I will link the first 3 parts in the comments below.
I have made several suggestions on what should be cut from the plot entirely, but here's what could be added to prop up the series more.
Have the moon cycle play a role in season one's plot
Given Amon turned out to be a self hating water-bender, have the moon cycle play a bigger role. There are rare events in the moon cycle outside of just an eclipse: https://spaceplace.nasa.gov/full-moons/en/#:~:text=There%20are%20a%20few%20different,Moon's%20many%20phases%20and%20types.
Have it so Amon has control over Republic City longer, have Korra and Mako find out Amon's secret and realize he plans to use one of the rare moon cycles in his final blow.
This would add needed tension and remind the audience of the bigger world of the avatar world.
Make Dreams Much More Important To The Plot
Dreams were shown to be important in Avatar, but played a minor role.
Dreams in the first series were shown to have connections with the spirit world.
Fixing what was broken
If you have to keep in the infamous kiss scene with Mako and Korra, have it be in a dream.
Dreams tend to be extreme exaggerations of what people desire or fears, making the kiss scene a dream would show that Korra fears her feelings towards Mako would ruin her friendships.
Korra's dream would warn her not to be impulsive, so to avoid this being a cop out show her actually learning from this dream hense why if she does still date Bolin she tells him she doesn't know what she wants and just wants to friends as I stated in part 2 of this series.
Making the horrible kiss scene a dream instead would also allow animation to be reused, have Bolin's reactions to rejection be the same in the dream and in person when Korra actually does the right thing showing parallels.
World building
Along with animals, music and sports, dreams are universal to all cultures and time periods.
All cultures in real life have different interpretations of dreams and mythologies surrounding them, using them to explain things before science was fully established.
Aang had dreams were he communicated with Avatar Roku and other spirits, repeat this with Korra.
Tarrlok and Amon's backstory was important at the end of season one.
While Tarrlok told it well, spilling out his whole backstory to Korra all at once seems a bit much.
Reuse half the backstory animation and set it up in Korra's dream, given the avatar has been shown in the past to connect with people threw dreams. Have Tarrlok finish explaining and give more context to these dreams.
Have the big relieve not only be Tarrlok and Amon are brothers, but Korra and Tarrlok have shared the same dreams.
That would be incredible! <- have the three share my reaction XD
Dreams can get away with a lot
Given a re-cut of this series likely won't be cheap without a lot creativity, dreams are a good way to also keep the budget low.
Given dreams are abstract this would allow for different art styles and could allow a low budget or even no budget.
The creators of Avatar are big fans of EVA Genesis, one character could have a dream referencing the end of EVA were the studio ran out of money and had to resort to using Crayola markers, (I'm not joking, that actually happened! Thankfully free drawing programs exist now if worse comes to worse for the re-cut!).
The only thing dreams can't get away with are cop outs!
I have to stress that each dream needs to be plot relevant. Use all dreams for character development, have dreams warn characters about danger and most importantly teach the characters something.
don't use them just as a "get out of jail card" for mistakes that were made originally.
See the video blow
https://www.youtube.com/watch?v=epsRdajaM2k&feature=emb_title
Humans and even animals have dreams and for good reason, being able to reflect on your day and emulate experiences you haven't had yet is linked to species intelligence.
https://www.nationalgeographic.com/news/2015/09/150905-animals-sleep-science-dreaming-cats-brains/
If it weren't from dreams, humanity wouldn't have made it as far as it has. That's why even in stories dreams need to be taken seriously.