So similar to The Delves you have lives instead of a timer but they could make a 4th slot on The Great Vault just for Torghast you have an NPC Companion in the form of Sylvanas Windrunner who can be Tank with Dual Daggers, Dps with Her Bow or go Wraith form as a Healer.
They can create their own Tier based loot system like they have done with the Delves bring back those passive upgrades you could get and have number of different Bosses and Maps and add more Bosses and Maps every season so it doesn’t get stale.
Then it ceases to be Choregast and isn’t mandatory but could potentially be a lot of fun and give access to some great loot alongside every one’s favourite Dark Ranger.