I think it's a great idea in principle, but that the rules will likely be tricky to figure out and probably need to be flexible.
One thing I'm thinking here is playing surfaces. Considering we're talking about a range of items with different sizes the playing surface would likely also be flexible, if there is one at all. So how does one define the movement of pieces? I'm thinking here if there is a convenient pseudo game board (or an actual game board of some kind) then just use that like a checkered tablecloth or the tile pattern on a floor or rug or something. However since there are many locations that lack that sort of thing, I'd suggest getting a ruler or measuring tape and using a defined unit of measure to define the movement of pieces.
As for guidelines on creating stats, well there's the obvious stuff such as pointy object has higher damage (of a piercing type if you go that specific) than a blunt one. Batteries have a large amount of "Mana," but can't cast most spells on their own. They probably can cast spells like acid (higher damage with lower HP), and spark (low damage unless enhanced by an accompanying item). You get the idea. I'd use stuff know about the physical object both for inspiration and also for restrictions.
Develop a point system that restricts: damage and health based stats by size and weight of the object, movement and attack speed based stats by shape and friction (a ball would be able to move further than a brick of the same mass), special abilities and "mental" attributes based on properties of the object's use such as a battery's voltage, estimated lifespan, whether or not it's rechargeable, etc.
All of those restrictions should be relative and estimated for ease of use on the fly.
With this information a bowling ball would be a massive and swift deliverer of destruction, a rake (this is getting particularly stretching) would have little ability to move but have an incredible attack reach and very high wide range damage however it would take several turns between attacks and the chance for very small units to avoid damage completely (happening to be in the gaps), pens and pencils would be able to mark opponents for an increased chance to hit and cause poison damage upon striking.
There's also the dynamic of adding and combining items for greater use, a pen and paper for an intelligence boost add a calculator for reduced spell cost, put the batteries into a laser pointer (incorrect size or type involves a small penalty) and you've got an unlimited range magic attack toss in a small mirror or other reflective surface and you can redirect that attack MUCH more easily.
All in all be creative anything that changes light, uses electricity, magnets, produces flame, etc is magic and treated accordingly. A lighter has a limited mana pool whereas a magnet casts a constant area of effect spell. A cylindrical object might have two different modes of movement: standing low move but stronger defense and attack, and rolling on its side able to cover more ground but can't crush its opponents with the same force.
Dang, I want to play this game now.