+1 to the idea, but add more potion effects. Honestly, I think it would be easier to be able to do /pot and then it brings up the list of Water Breathing, Night Vision, and other effects. Maybe it could be every rank starting from NV gets a new potion effect, but not something very powerful.
Exclusive = Night Vision
Elite = Fire Resistance (Fits with all of the Fiery perks elites have)
Supreme = Water Breathing
Ultimate = Haste (Though this may sound very powerful, ultimates don't have many perks at all really. This could be like the /dis vein, or the /effects vein, where every rank receives a new one, starting at X rank- for disguise Premium and effect VIP.)