Same for me!
*SPOILERS*
Some quick things I would do:
1) Don't make the alternate universe purgatory. Or at least don't set up an alternate universe storyline since the Season 5 finale that's somehow going to influence events in the current day to stop The Man in Black when it really has nothing to do with the story at all, takes at least fifteen minutes out of every episode just to set up fanservice, and plays no character strengthening role like flashbacks did or flashforwards eventually did. At least the flashforwards led somewhere with plot purpose and relevance to the story at hand. It's was a great idea for Lost originally, when the character stories mattered, but it's lame bull**** and terrible writing the way it was brought about and set-up. And they're in heaven together because of the nuke? Really?
2) Actually make it all about the characters. The creators can't say the show was all about the characters when at least half the characters are given the shaft.
Sayid: I died, now I'm alive. I'm also going to turn evil because of the sickness so I must kill Flocke before he talks to me. Whoops, he's spoken to me and now I no longer care if I kill a ton of people and the guy that tortured me. Woe is me. I'm so apathetic, I'm now speaking with a British accent. Time to kill Desmond? Okay. Hey, Desmond. What's that? Words of meaning? I'll go with my fellow Lost mates into the unknown even though I'm supposedly evil. I can run our of here with this bomb, but I don't know how long the batteries will la-
Sun: Have you seen my husbant? Have you seen my husbant? Have you seen my husbant? Have you seen my husbant? <Oh no, the smoke monster made it so I can no longer speak English for some reason. The only way to save me is to find my husbant. Have you seen my husbant?> Hey, hubby, I hope these pylons don't kill us when we hug! What's that? Oh, Jin, save yourself. You are so noble and loving to stay and drown with me. I will never forget those I love. I love you so much, Jin.
Ji Yeon: Where's mommy?
Claire: I'm crazy! You all forgot about me! Lookit mah baybeh! Isn't he the cutest little goat-skull? Locke is my BFF! The others are bad people who took mah baybeh! Kate came back for me even though she elft me here? SHE STOLE MAH BAYBEH? Whatever, I'm just gonna mope now. Oh we're leaving? K. Let's be lesbians in the afterlife, Katie.
Michael: Sup. I died.
Kate: I saved a bullet for you!
Richard Alpert: I'm not really all that special. I just showed up one day and now I'm ageless. I'm really not as powerful or magnificient as you once thought I was. Now my hair is turning grey.
Jacob: I'm not really all that special. I was just born one day and a crazy lady adopted me and my bad twin. He's evil because mom says he is. I'm kind of a dick and really not as powerful or magnificient as you once were led to believe.
Barry: I'm the man in black, the smoke monster, Jacob's brother. I've been tormenting this island for millenia and now I've taken over Locke's body. All part of the master plan to find a loophole and leave this island. Why? Why not? There's been some nice writing about how I may not be a complete black hat in this game and my motivations are just a depressed manchild curious about the world and trying desperately to understand why my mom's dead and get away from my crazy-ass fake mother. But apparently, nope, I'm just straight up evil with no redeeming qualities unlike all the other murderers and torturers and *******s who permeate the place.