Superman - Give Superman and Lois their own child with Mxyzptlk's help, just as Rucka was hinting at in his run. Also, bring back Conner Kent and Matrix, and make them, Power Girl, and Steel more of an extended family to Clark.
Batman - Bring back the Gotham Central police officers and use some of them instead of dealing solely with Gordon and Bullock. Have Dini write everything. Make Tim his own person again instead of a miniature clone of Bruce.
Wonder Woman - Make her less of a ******. I don't really mind the Diana Prince thing, though. I even kind of like Nemesis. Bring back more of a mythological influence alongside the political espionage stuff, though.
Martian Manhunter - For God's sake, put him on the JLA. Agree with Anubis on the rest: keep the costume, lose the emo. Though that seems to be the way they're going anyway.
Green Lantern - Ditch Hal and the Parallax fear demon, make John and Guy the sector Lanterns for 2814, keep Kyle as Ion and continue with the "troubleshooter" role he's got, and give Alan Scott more of a presence alongside Kyle. Everything else is fine.
Flash - Waid's doing pretty well.
Aquaman - Reveal that the Aquanewb is just a piece of Orin that splintered off, rejoin them, keep the water hand and Aquanewb's costume, keep the Arthurian, magical overtones, return him to his rightful place as an arrogant yet noble king, add Sub Diego to his kingdom, restore Tempest to a powerful sorcerer and make him Orin's chief advisor, keep Lorena around.