I think there should be some suprises or rewards to make ppl play the game slower, thus longer. I think the time should play some important role about improving some aspects like accuracy and speed or even new moves with the weapons. It would be like "The more time you spend with characters, the more they improve themselves."

KOTOR already had that to an extent. My girlfriend whipped through the game slowly, but had a weak character. I did every sidequest, and looked for every item in the game. Thusly, by playing slower, I had a more powerful character (as well as a more rewarding experience).

yet there should be much more main and so side quest to make KOTOR II good

I agree that longer gameplay would be good. I think most people would.

 

However, the devs have stated that length of play in KOTOR:TSL should be similiar to KOTOR.