I was just thinking, it would be pretty cool when you reached the end of your story, and if you had enough karmic points, you'd get the option to switch over to the other faction.
For instance, if you were dark enough as a Jedi Consular, you would eventually be welcomed into the Sith army as a dark lord and your class would switch over to its equivalent. You could even get a special title like "The Fallen".
Or "The Redeemed" for Sith turned to the light.