After thinking about it, here is who should return after LS Male Revan and LS Male Exile.
Orignal Party Members from KOTOR and TSL
Carth Onasi - Temporary Party Member to play with at the beginning for a tutorial.
Mission Vao - She could see return to a rebuilt Taris along with her brother.
Zaalbar - Be the new Chieftain of Kashyyyk.
Bastila Shan - As a full Party Member, but not as your Master. You could say she has sort of lost her connection to the Force. And she wants to find Revan.
T3-M4 - You obviously need him to help find Revan and the Exile.
Canderous Ordo/Mandalore - A cameo, but not as a Party Member.
Juhani - To avoid confusion with the Dark Side, you could say she died on Katarr.
HK-47 - Same as T3.
Jolee Bindo - Say he died of old age. But include him in a holocron.
Kreia - She can't return, because she doesn't like the Force.
Atton Rand - Should return to find the Exile. Maybe he could fall in love with Bastila.
Bao-Dur - A cameo, helping the Handmaiden on Telos.
Handmaiden - Should return, but as a cameo with Atris's role. She should tell you when she last saw the Exile.
Visas - She should also be a Jedi Master.
Mira - Should return as a Jedi Master, but not a Party Member.
Hanharr - Mira should spare him on Malachor as it's the Jedi way. He should return to Kashyyyk.
G0-T0 - Can't return because he died along with the Remote on Malachor.
Characters that appeared in KOTOR and TSL
Dustil Onasi - Once finished with Carth, he should replace Carth.
Yuthara Ban - Should return to help you.
Kelborn - I can't remember where I saw a suggestion for Kelborn, but I thought it was a good idea.