Idea for passive that is only up for 5 second every 10 seconds, which grants bonus on-hit damage

E.g. Passive grants 30-140(based on level) + 40% AP magic damage on-hit for 5 seconds, at which point the bonus damage is disabled for the following 5 seconds.

I've suggested a fairly high scaling because It should be the primary source of damage for whichever champion has this passive.

I feel the playstyle would be really fun and challenging with clear strength to weakness identity.

My reasons why are nothing special, Just an mechanic that I think would be healthy for a new or reworked assassin in the future update.