User blog comment:NinjaWolfy11/Discussion: What should be done about the mobility issue?/@comment-4636093-20120906001845/@comment-217.121.187.123-20120906081903

That item would make Riven totally unviable. She'd just have no shield, and only about 30-40% of her normal damage. This alone is reason enough to not make such an item. The same on champions like Lee Sin.