So a thrown glaives wouldn’t take anything away from Havoc as it only has throw glaive and that can be used to setup cleave and what not all depending on your spec as you know. I do not see how throwing glaives would take anything from havoc you would be infusing void magic into your glaive and throwing it for your abilities and what not.
Way back rogues could throw daggers all 3 specs could IIRC and you had a throwing dagger that you had to equip that was ammo like hunters having to equip arrows and bullets to use their bow or gun. But blizzard killed that because it was too hard for people to remember to bring arrows bullets or another throwing dagger.
Point is that that a thrown weapon spec would be unique and interesting to see imo.