This assumes the Original Cast returns; so Billy Dee, Mark Hammil, Carrie Fisher and Harrison Ford are back. Since i'm unsure of exactly where this will take place I'm gonna list a lot of casting choices

Jaina Solo - Jennifer Lawrence

Jacen Solo - Andrew Garfield

Anakin Solo - Nathan Kress

Ben Skywalker - Alex Pettyfer

Mara Jade Skywalker - Jessica Chastain

Darth Krayt - Jeremy Irons

Onimi - Hugo Weaving

Darth Sidious (Reborn) - Tom Hardy

Thrawn - Jamie Foxx (Physical) Michael Ironside (Voice)

Shimrra - Ryan Gosling

Lumiya - Elizabeth Banks