I like the idea of lending companions to other characters in my legacy ala Dragon's Dogma (the pawn system).
Imagine this, my Sith Warrior decides to lend Jaesa to my Sith Inquisitor to help him determine whether a Jedi is faking their decision to defect to the Sith. Mind you, the issue here would be dialogue - responses for 8 different classes would take time. And most people only ever finish their companion convos with 2/8 classes, that's only 10 companions out of 40. So it would have to be a Cartel option or EA probably wouldn't be interested