In the out of no where department...Jessica Biel appears (not confirmed yet) to have been offered the role of Viper (don't remember hearing anything about Viper being in the early McQuarrie drafts so this might be a newer role if true).
http://www.comingsoon.net/news/movienews.php?id=92525
I'm not the biggest fan of hers but I have liked her in some stuff, have to admit that she would be an interesting Viper. Obviously since Viper is a Hydra agent (currently Madame Hydra) this might have to be tweaked since Hydra is owned by Marvel Studios.