These kids after Malaks death were raised by what remained of the Sith. Fed lies about what had happened to the Sith Lords Revan and Malak. They tell them that Bastilla killed both Revan & Malak. Saying nothing of Revan's crusade for the light.
These lies make these Twins angry and want revenge on Bastilla for what they think she had done. When the twins are of age 15-18 they then want to pay bastilla back. A small group of sith and them attack a ship flying to the outer rim on a good will mission that has Bastilla aboard. They then board and locate Bastilla and kill her. On her death bed she tells them of Revan that she is not dead. And tells them to track down a Republic Commander called Carth Onasi.
After hearing this they realize the Sith lies and leave the sith. They then fly a ship to Telos in search of Carth. They eventually do and he tells them he is not entirely sure where Revan is but he has some idea of how to find out. He then tells them that they need to recover the Ebon Hawk and locate the Crew which helped Revan defeat Darth Malak. The owner of the Ebon Hawk is on Dantoonie at the newly rebuilt academy there. After he has done so to meet him on at the location he last saw Revan.
They travel to Dantoonie and (Main Character from Kotor II) tells them that if they wish do find Revan he wishes to help. Now they just have to locate the old crew of the Ebon Hawk. Mission, Zaalbar, Canderous(Mandalore) and Jolee. Juhanni, Hk-47 & T3 M4 would already be at the academy. Each crew member would take you to different planets from Kotor I & II. Mission would be on Nar Shadaa. Zaalbar where else but Kashyyk. Canderous of course Dxun. Now Jolee he's tricky where would an old senior sick of the forest go for retirement. I guess Manaan which was devastated by the Jedi Civil War.
Once you find all the crew you them meet Carth. He think he's figured out where Revan may be. You then do so. You then have to go through a few battles. And finally you find her. Its a happy reunion. She than reviels what brought her out to where she is. A living Sith. Not just a any sith but a member of the Sith Race.
You then fight this creature or for darkside I guess you join the beast. In doing so you then have to kill the entire crew that brought you took out here.
Once you kill this beast (for LS) you than go back to the location of where the star Forge once was and you and Revan talk to Malak and he explains why he never told Revan of her kids when he revieled to her who she really was when she had amnesia. If you join the beast (For DS) you than take over the entire galaxy.
This may not appeal that much because than it is locking in the fact that Revan was a girl. It also requires you choose a name for the Main from Kotor II. But other than that it wouldnt be bad in my mind.