What if Crits weren't chance based but a resource bar?

There's been a lot of complaints about crit in the past. Some of it because of randomness. Some of it because too much burst damage.

That got me to thinking, what if riot converted critical hits from a chance based system to a resource based system. While attacking in combat, each hit fills up your crit bar. Once it is full, your next attack crits. If you leave combat, the bar starts to deplete. Items therefore would be rebalanced make the bar go up faster or slower. Another thing that could be done is make the speed of the crit bar fill based on how tanky the target the person hitting is. Tankier targets generate more crit bar and squishier ones generate less. This would let ADCs tank bust like they need to while giving squishy champs a chance to react.