After an incident with Dr. Hugo Strange, Lucius Fox, who in the comics has no idea that Bruce Wayne is Batman, decides that Bruce Wayne needs protection. For obvious reasons, Bruce doesn't feel he needs it, but Lucius insists. So Sasha Bordeaux is hired to become Bruce's 24-hour bodyguard.
This makes things a little tricky, since the times Bruce wants to sneak out to become Batman are the exact times Sasha wants to stick closest to him. After a number of incidents where he disappears in the middle of the night, Sasha becomes suspicious and eventually does discover his identity. Because of some kind of bodyguard code, she keeps his identity secret, but insists that she must extend her protection duties to his time as Batman. So Bruce puts her through grueling training to get her in shape to take on the dangers he faces, and she starts accompanying him as a sidekick of sorts.
It's at this point that the Bruce Wayne - Murderer? story kicks off. Batman and Sasha return to Wayne Manor after a night of crimefighting to find the body of Vesper Fairchild, Bruce's ex-girlfriend. Their only alibi is Bruce's identity as Batman, but both refuse to say anything. Lacking any other explanation, Bruce and Sasha are arrested. Sasha appears to be killed in prison, but her death was faked as part of her recruitment into the secret government organization Checkmate.
Pros: She's a strong woman who can hold her own with Batman. Her role as Bruce's bodyguard made for some fun situations where Bruce had to improvise ways to change into his costume, or stop a villain without becoming Batman.
Cons: There would have to be a whole new introduction scenario, since the movie version of Lucius knows Bruce's identity. And even though Sasha was a pretty good character, she was mostly introduced, I think, to set up the Vesper Fairchild murder story.
How I'd do it: Instead of Lucius Fox doing it, have the FBI show up and send Agent Sasha Bordeaux to provide round the clock protection for Bruce.
Casting Guesses: Jessica Biel always look like she could kick my ass without breaking a sweat, which seems bodyguard-like.
Verdict: It's highly unlikely. Sasha's a relatively recent, relatively minor character, who's probably more associated with Checkmate than with Batman. But you never know, I guess if there's a story that works with a bodyguard, she'd work well.
After The Scarecrow, Ra's Al Ghul, The Joker, and Two-Face, who should be Batman's next enemy in the Batman Begins/The Dark Knight series? Well, as of now we know that Tom Hardy will play Bane and Anne Hathaway will play Catwoman.
Check out the master list for all the villains covered. I've pretty much run out by now. Obviously, there are more Batman villains, but not any of significance that I know of. As of February 2009, no one is confirmed as a villain. Not the Johnny Depp Riddler, not Phillip Seymour Hoffman Penguin, nobody.