I've added the Aether Gloves (all ranks) at first in melee_weapon, then I tried projectile and armor. None of these allow the Aether Gloves to level up. It'd have to be a melee weapon for it to work as intended (since they add damage on their own).

What I also found out is that while ranged weapons do gain a damage bonus per level and armor an attack reduction per level, melee weapons somehow do not gain any levels. Is there a way to try and debug this?