What if lifesteal were a flat amount instead of a percentage?

I was thinking what would happen if lifesteal just gave a certain amount of health on-hit to make things "burst heal" a bit less. Like, heals 20 health on-hit with reduced effect on minions and monsters... Maybe have increase the potency of lifesteal slightly or something. Have completed items that have 10% lifesteal give some more health instead of staying the same. That would make more bursty champs focus more on damage instead of sustain, because when I thought about it, on-hit champs are the ones that need to survive longer since they fight for longer at a time, while burst champs want to end fights as fast as possible. It also keeps champs that use crits from RNG healing a bunch at once. Just thinking it'd be interesting.