One thought I had when I was still considering a Glove of Storing PrC was the ability to using it to store intangible things (such as storing fire and releasing it later as a ranged touch attack, or storing smoke or mist to produce a cloud effect). Maybe allow the storage granted by your cloak of useful bags of holding to capture certain intangible things like spells, gouts of flame, air, thoughts, etc. Then instead of pulling a wand, a warrior pulls a stream of positive energy or some such.
Make the damage, healing, and/or area affected scale with level, and maybe add different effects per level (like the ability to capture a stench to produce a stinking cloud eventually).