They should have a Sith Lord from the future who is controlling a Sith Lord in the present time. (about 10 yrs. after the events of KOTOR II) The Sith Lord who is being controlled becomes the religious leader of a planet. He/She eventually interjects himself into the government and becomes the president's closest adivisor. He/She then kills the President and assumes control of the government. The people love and embrace this. The people of this planet then start a war of conquest. They start attacking other worlds and take them over one by one.
Just before these events, a scientist discovered the technology to allow anyone to use The Force. Everyone now uses The Force to help with daily tasks. It is integrated into almost every aspect of life. The Republic has created schools on many different worlds (some even on space stations) to train soldiers in Force combat. The Jedi are obviously not happy about this, but there is little they can do. Your PC starts at one of these schools.
Eventually you (and your party) confront the Sith Lord and fight him. You win, but of course realise that he is only a pawn. In fact, he isn't even capable of using The Force without assistance from technology. He was unable to control his actions and deeply regrets them. He allowed the Sith Lord from the future to possess him, so that the "future Sith Lord" wouldn't find his real target. The scientist who created the technology to allow anyone to use the Force, helps you find a way to go to the future and defeat the Sith Lord there.
"...but Mom, all the other kids are doing it!"