I would like to see that KOTOR 3 take's place a 1000 years later than KOTOR 2. This way you can use a lot of new ideas and storyline and still maintain quite a distance from episode 1 (about 3000 years).
I liked the idea to create a new jedi order as a main quest, so you can explore many different world's to search for fellow jedi's. A greater world diversity would really make the game better than KOTOR 1 & 2.
But how to start the game? A Fable kinda approach meaning you start at a young age en discover you have strange feelings (ta ta! the force) just before something bad happens. After a few small quests (great way to include a tutorial) you grow and a few years later, a friend is attacked bij some alien thugs and you accidently Force-pushed one of the tugs while you try to defend your friend. Finnaly a cloacked man approaches you and your training begins (choose class, bla, bla, bla).