Essence Reaver Ides

I was reading one of the essence reaver posts that said that essence reaver gave mana steal. It restores mana upon basic attack, but that's technically not stealing mana. But what if essence reaver did steal mana?

Essence Reaver (new) 80 AD 10% life steal 10% cooldown reduction (New) Unique Passive - Mana Steal

Takes 6% of an enemy champion's max mana (or possibly resource) upon autoattack, depending on their current mana. Restores that amount of mana or 2-8% of your max mana, depending on current mana, whichever is greater. If a creep or monster is attacked, it restores the max mana value.

This would give essence reaver a reason to be purchased by poke champions or caster adcs like . The number might have to be adjusted, but the concept is that buy poking them down, you make them vulnerable to ganks by your jungler.

What if the enemy does not have mana?

Maybe some resource drain, but that would be hard to balance.