Your throw glaive appearance is now what ever weapon you have equipped.
The 1H from Grong I have equipped would look pretty derpy.
You mean pretty amazing.
Nah.
This is better and easier to code since it is a copy/paste job from the Warrior glyph:
Your Throw Glaive ability causes the appearance of your Throw Glaive to change to that of a random weapon from your bag for 10 min.
So if you have a huge collection of 2H green items, it would be funnier to see a 2H Axe or Hammer flying across the room instead.
So, abilities are difficult to do this with. Spell animations, as far as I can tell, aren’t really designed to be super-dynamic in visual. Glyphs add a handful of possible variants, but that’s about it. That’s why abilities using weapons (Throw Glaive, Poisoned Knife, Judgment, Heroic Throw, heck, even old school Fury of the Illidari, iirc) typically use a static animation for them, because otherwise they’d have to make a variant of the spell for every possible weapon model or rejigger the entire spell code to tolerate hotswapping models in the animation.
At least, that’s what I’ve gathered from the way spells like they have been implemented in the past.
That said, they could probably do it if they hacked it a bit. See, Felguards can have variable weapons equipped via a glyph, so clearly hotswapping them on NPCs works. So what they could probably do is recode Throw Glaive as an invisible NPC holding the glaive in the same position and spinning rapidly while shooting towards the target. The same could probably be done for Heroic Throw, Poisoned Knife, and Judgment (for all 3, the invisible NPC would be doing somersaults while flying, which would be amusing to model).
I doubt it’s seen as worth the manpower commitment, though, especially with how skeleton the team working on WoW appears to have become.