cut out the love triangle (quadrangle? idk) and replace it with korrasami bc i think they make the best couple even though it's way too early for lgbt romances to happen in children's shows. just personality wise i think they make the best fit.
but without the whole bullshit they would have more time to develop characters and not cram everything into the last five minutes of the last episode.
more development for bolin and more bonding between him and mako and korra bc they're all supposed to be like best friends yet we don't see that happening enough.
trim down the pro-bending stuff bc it was cool but it wasn't that interesting and it felt below the avatar. i'm not saying it should have been cut out completely or that bc korra is the avatar she can't play in pro-bending, but rather that it's really stupid that a sports game was the main focus of so many episodes.
give iroh a different va or at least deepen it for ******** sake he's like almost thirty but he sounds sixteen. i love dante basco but holy s**t he sounds so young.
i mean listen to this clip that was deepened using audio software. it doesn't sound perfect but professionals could do this easily.
http://soundcloud.com/matt0753/iroh-ii-deep-voice/s-UpqTm
also i would cut out the incorrect usage of "electrocute". that s**t got on my nerves hardcore.