Incorporate them all into categorized separate items. You could have a charge up system to where if you charge an elemental shot off, depending on the charge time, it will change the kind of attack you use:
Charge <1/4: "Rapid shot" Weak but volleys magical bolts. Slight spread
Charge 1/2: "Single shot" Normal Damage. Accurate.
Charge 3/4: "Effect Shot" Elemental effect (Burn, Freeze, Poison). Normal damage + effect
Charge Full: "AOE" Elemental Bast from player. Damage radius + pushback.
A system like that would require a maximum of 5-6 items with 3-4 spells each depending on what element or magic types you'd want to use, would allow for custom wand models to differentiate magic types, and would add a level of skill but would also add to gameplay, not hinder. It would more than likely need a charge bar with segments so players know what level of charge they are at.
My idea takes more work sure, but if you want to make a mod that will be used and not forgotten in a week, I suggest you take the effort to do something universally useful. Please don't ruin this idea with /commands..
That seems really unnecessarily complicated. The charge thing used by holding down the button should affect the size of the projectile and spell type should be what you're binding it to. I seriously think having multiple items is kind of a bad idea, those extra slots should be used for potions, runes, artifacts, etc. If you're using the emote-bind system, then you can set your binds when you first join the server and never have to set them again, because I think 6 (if you use the light key too - you could even extend it to 7 with the sit keybind) easily accessible spells is plenty - 1 fire, 1 ice, 1 poison, 1 stunning, and 1 damage spell (mind you, that's more than your inventory, so you can't really complain when it requires no extra effort), and when you need something really specialized outside of combat for puzzles or something, then you can used something like "/cast <spellname>," and for frequent visitors you may be able to use "/bind save" and "/bind load"