I believe that K3 should start with a cutscene showing Revan wandering in the Sith space and finally being ambushed by the Sith.
The Sith recongize Revans potential in the Force and try to break him. They are half succesful when the exile steps in and the fight begins. Unfortunately both are caught and are placed in prison.
Then during the dialogue between the exile and Revan, you get to set-up the game according to your precvious games (k1 &k2). Also at this point you get to a screen and try to re-create Revan and the exile.
If would be "interesting" at this point if the Sith would cut you from the Force (if Vrook could do it then there is no reason the Sith can't).
So basically you can start as a Forceless Revan or Exile (and this time you can choose to remain so) who tries to esape the Sith.
It could be that during the escape one of them dies so the other can escape and warn the others of the Siths' power.
This could create some tension with other party members (ie if Revan dies, then Bastila and Carth blame the exile, or Revan is blamed by K2 members for the exile's death.