1. Create glamered cosmetic light crossbow. I used Morninglord's Light Crossbow, Sureshot and Legendary Nightshade Shooter.
2. Apply glamered weapon aura. I tried Enhanced Acid, Enhanced Fire and Holy all with the same results.
3. Equip cosmetic light crossbow. The correct cosmetic weapon appears. However the weapon aura appears momentarily to the main hand (but not the off hand), then fades away from view.