Kuznetsova...once she learns to deal with the pressure of finals, could become a real force. she truly has a lot of tools at her disposal, she just need to learn some meditation techniques or something to keep her in the zone when she is in a key match or critical moment of a key match. I don't think it would hurt her to get in a little bit better shape as that would help her movement on the court. She has some really good weapons, she just needs to sort her head out and improve her fitness a bit.
Safina..sort of the same without the getting in better shape. Just learn some relaxation tips and to raise your game in big momemts. Safina is however, new to the upper echelon so nerves are to be expected, now that she is so close to number 1 I just think she needs to figure out a way to channel her nerves into something else, to motivate herself in big matches, as her three biggest endeavers (Olympics, RG, AO) were all finished in mighty big flops. She plays well when the chips are down, she needs to transfer that and use that all the time.
Sharapova needs to develop the rest of her game, she has a mighty serve, powerful groundstrokes and a pretty solid forehand, she could probably learn to slice and spin the ball, and she needs to stop swtiching to hit a lefty forehand whenever her backhand is under pressure because that shot always comes off awkward when she tries it and 85% of the time she loses the point shortly after trying it. Also...she is someone who, if she wanted to, could be ademon at net if she could get comfortable up there.
As for the others, some are nearing the end of their careers (Mauresmo, Petrova, Dementieva, Schnyder) and thus really don't have the time to fix everything. some have quite a few things to fix ( Bartoli, Hantuchova, Vaidisova, Chakvetadze) that it is hard to say where to start. But if they really worked at it, any of them could move off the list and eliminate the things we have criticized them about.