Rapid firecannon

This recently added item is interesting. It works like statikk shiv but increases the range of your auto attack instead of dealing aoe damage. Cool!

However I have one question. Why can statikk shiv proc crit but rapid firecannon proc can't? I get it that rfc already has double the base damage but still I feel like there should be some kind of a bonus when critting with the rfc proc. Maybe an instant 30-50 charges for the next proc so you can have long range attacks more often. Also wasting the proc on minions feels really bad since it's not really meant for that (unlike statikk shiv). Maybe the proc could not be used when attacking minions within your normal attack range. Or again maybe part of the charges could be refunded when killing a target with the proc.

"Moving and attacking generates Energize stacks, up to 100. When fully Energized, your next basic attack gains FIRECANNON and deals 50 - 200 (based on level) bonus on-hit magic damage. Critically striking or killing a unit with FIRECANNON refunds x amount of Energize stacks."

Would this be too oppressive?