It is possible, I even have the "base code" to do it that way. However, to do it, I would have to re-write all item triggers. that is, 140 item combos. Right now, they are short. the trigger DOTA uses, is about 3X as long, per item creation. The ~150 pages that are my item creations, would become 450 pages of text... Not sure the last time you wrote 450 pages of text... but it isnt fun at all!
Really, it is laziness. It is a good system, but, to save you guys the 1 second it takes to drop an item, or simply to use your peon... isn't worth the time it would take me to re-write all of that. I could prolly add 30 more skills in that time... or 50 more heroes... or create 3 full game modes, Or fix one bug...