As if dragging Maul from the grave for part 1 wasn't bad enough.
Let's have a Ravan clone with Luke, Supershadow and Anikon dna! Uberpwnage. [/sarcasm]
But seriously. No ancient Sith Lords. Referencing is okay, blatantly raping canon (what they'll probably do) isn't, imo.
If you'd want to add something, maybe have Galen visit Korriban and some tombs, like Kotor did.
Maybe they could intertwine with the Swtor team to sketch Revan's past. Some clues in this game, some clues in Swtor...but LA wouldnt do that.