Ability Crit Items

So currently critical strike has no use on an ap champion aside from a few hybrid fringe cases like teemo. But essencially there are much better items out there for these types of champions. The main reason for this is there is not any items to back these kinds of builds or abilities that benefit from both crit chance and ap. But why can this not be a thing? Would allowing mages to crit with abilities really be that bad of a thing if there was a proper itemization to support this kind of gameplay? Sure the ability cannot have the 200% base damage multiplier of a basic attack but it could do something like 125% of the abilities base damage and still not be overpowered by any means. A couple concepts for items to support this kind of gameplay would be an item that perhaps grants bonus ability power based on your crit chance say givs x%bonus ap where x is equal to 1/3 of your crit chance or something maybe even 1/2 or something. Another item can be something similar to but that gives energised offensive abiliities bonus range or perhaps something that gives them bonus aoe. Another item that gives your abilities a chance to crit for 125% of their base damage or something based on your crit chance. Another item that perhaps like but grants ap instead of ad. with ap instead of ad and allows your crit to do bonus ap as physical damage or something.. These kinds of items would essencially add a degree of unique build options for mages and would have the downfall of low base ap but the potential to deal large amounts of damage if teh crit is to trigger. perhaps more damage then traditional ap items but this is only if the crit is to trigger. It would allow for a unique niche style of build for various ap champs and a different build path from the traditional and for mages the current build paths are quite cut and dry with little to no variation outside of do i build straight ap or do i build ap with a small amount of defense? Whereas Ad champions have a large variety of buildpaths and unique/gamechanging items. The point is why not even the odds?