"Life Guard" (Passive Item Ability)

What do you think about giving an item an ability called, "Life Guard", that reduces or otherwise limits the amount of Spell Vamp and Life Steal that works on the player? It would help reduce the effectiveness of full lifesteal/attack damage builds in the late game (I'm looking at you, Master Yi with Highlander activated). I think it could be an incredible defensive ability, and to put it on an item similar to Randuin's Omen would help make tanks more effective against these builds in a one-on-one. I'm open to ideas and comments.