Great question! A number of players could win, but all have points against them as well.
I still think Serena wants another French before she's done and if she's fit and focused, I can see her winning, but we always say that. But, it won't be easy. Something always seems to happen at the French, whether on her end (nerves, simply not playing well) due to someone else (simply, a player playing better). I give her a good chance, though far from certain.
Sharapova - She's won it, so will be even more comfortable. She annoys a lot of people, but she's a hard worker, unbelievable competitor, and great ball striker. If she can minimize the serving woes and dictate points, she has a great shot. But, movement issues persist and if she has an off serving day (at least more off than usual), she won't win.
Azarenka - powerful, consistent, good defense. Slam champion confidence (which has been confirmed with her second slam). Not sure what form she's in though. I trust she'll be ready for Roland Garros.
Li - good movement, serve, power, past champion, has learned to (sometimes at least) be more patient and construct the points a little more. Has the game, but can be inconsistent and sometimes (but not always) mentally flighty. Depends on her draw, depends on her mindset, but there's at least a chance.
Kerber - quirky player, great offensive/defensive combo, can annoy people. She hasn't been as sharp lately, but she's performed good to great in Slams dating back to the 2011 USO, her break through. Not picking her, but if anyone is going to be a first-time winner, I'd pick Kerbs.
Kvitova. Much like Soderling, clay can actually assist her ball striking - she has more time, she's tall, so the ball is in her strikezone (or at least less out of it compared to other players), her power, while not as penetrating, is still effective. But, her mediocre movement can more readily be exposed. Plus, hasn't been really playing that great. If she shows improvement during the rest of the clay season, an outside chance. Draw dependent.
Radwa. We love her variety, we know she can frustrate opponents. But the crap second serve and lack of firepower will expose her again. A deep run, sure. A win, no.
Stosur. She likes clay and if she plays to her potential, she has an outside chance. But, that's a huge "if". As always, her mental issues will be tough to overcome for seven rounds. Maybe she'll be more relaxed with low expectations. Then again, she hasn't done anything this year. She'll need to do well pre-French and gain confidence.