The Tinker Tool

With the recent changes in league of legends, There have been several new items added. However, most of these items only benefit champions with Attack speed or attack damage scaling. This here is a suggestion I have that would benefit mages, both physical and magical. However it wouldn't effect marksman or auto attack based carries because they don't rely to heavily on spell damage

The item in question is the Tinker Tool. build goes

+ + 1250g = total combined cost is 3800. same as death cap

70 ad 70 ap 15 armor pen 15 magic pen unique passive : every forth unique spell has its damage converted to the opposite damage type excluding ultimate spells

Thoughts and opinions on this item concept?