I'm wondering if I've missed anything already in the rules, but I've been looking at some kind of mechanical method of reflecting the "schtick" of the various Sith Lords; the way the operate and the effect they have, from where they draw their strength, etc. For example:
Darth Sidious - all about deceit, deception, clouding the minds of people around him (reflected in his name: inSIDIOUS), manipulation, etc.
Darth Maul - all about unbridled rage and destruction; not even hugely strong in the "wizard-y" aspects of the Force, but a nightmare in battle.
Darth Vader - all about fear; terrifies those around him, breaks them down with intimidation and terror. The novelisation of "A New Hope" describes his first appearance in similar terms to what we see in "Rogue One" (sans the actual awesome carving up of the Rebel troops), where hardened Rebel troops break and run in horror at the sight of him.
I'm trying to think of a way to "personalise" different Sith in such a way. Any ideas would be welcome.