Bring the BoBs back! I like the idea a lot, but tweak it a bit. No exotic engrams, no golden glow. Let them have their own Grimoire Cards, a BoB achievement to kill them all and just like a VIP event, without the event indicator. Spawning on several possible location, sometimes with a group, sometimes alone. The Legendary Armour set is more fun. Or have them drop parts, which trigger a questline. Which can award you an Exotic weapon and an emblem or shader. Maybe a pure gold shader.