How bout allowing all spells to be cast while

How bout allowing all spells to be cast while moving but when you move the power of the spell is nerfed by a very large amount. IE. Instead of a Chaos Bolt hitting me so hard it makes me think about rerolling classes to... if I can apply enough damage he will have to move so he po world of Warcraft doesn't die... Instead of loosing the cast he is still able to get it off but at reduced damage.

Rolling Nerf btdubs: IE if I move for the entire cast time of a Chaos Bolt you only do say... 10% of the damage of what you would have done if you just stood there or say I only moved for 1 second it reduces the damage to about 40% or something along those lines.