What you can do with wands (or rods) is to make them off-hand equippable, and such that they must be equipped in order to use them or gain their powers or abilities. For example, an equippable Wand of Missiles must be equipped in the off-hand in order to use it to cast Magic Missile. As far as I know, that’s pretty much it.
I did this a dozen years ago, so I don’t remember exactly how it’s done offhand (pun not intended :)). But I use these extensively in Sanctum of the Archmage. (The modules’ most important item, the Control Rod, is implemented in exactly this way.) I’ll go look at the baseitem.2da entry in Sanctum to remind myself how it’s done and follow up.