(yes-yes, another suggestion
Mythic Legendary event. Reminds Malak's event, but for Darth Sidious(ep.3)
1 Tier: You need Master Windu, Fallen Anakin(new HJ character) and 3 (GR) Jedi to 'defeat' Darth Sidious.
2 Tier: You need Goblin(GMY) and probably Shaak Ti or Master Kenobi(some new Legendary Master) and 3 GR characters.
Of course pretty high difficulty(Mythic Legendary all right) but a bit less random the Malak's