There are rulesets for that, as well as some fan made ones for... "interacting" with them. ;] It just dosen't feel right when you have to hit things for it to work. That's functionally lifesteal. Everyone can have lifesteal.
Nothing stopping us from having both. As far as I can tell, the game should be capable of supporting something like that. That's also a cool idea, though I'm not really certain how viable it'd be from a monetization standpoint. Regardless of all other concerns, the big point here is that currently the game underutilizes…