Champion Ultimate Concept

Ability Summary: 10/20/30% debuff to attack speed or movement speed that lasts either until the champion is fully healed.

I was watching some league videos yesterday about how a champion that gets behind in the laning phase of the game can be of some use later in the game with a utility ultimate. And I realized that an ability that reduces an opponent's attack speed for an extended period does not exist.

So what I have thought of is an attack speed debuff that would work on a single targeted champion. I wanted the debuff to last for a significant time so as to hurt the enemy team significantly in a team fight. As a way to have that make sense as far as an explanation for it, the attack speed debuff would be due to the arm or hand being cut off. Although that then poses a problem for champions that don't have arms such as kog'maw. In which case if I want to stay with the arm cutting off idea(which i personally think is cool) such champions would have a leg or foot cut off, reducing their movement speed as well. Other champions would also need exceptions like anivia, galio, and vel'koz; in which case they could either be immune to the ability, have it cut off one of anivia and galio's wings and have velkoz immune, or replace the limb severing idea with a magical effect.

The ability(left as a limb sever) would also have to do damage since a limb is being cut off, although to keep the debuff as the main reason for the ult it shouldn't deal a lot, having damage similar to a marksman q, w, or e ability's damage. Personally to keep the damage down so that it maintains as a utility ultimate I would say no chance of crit on use, but due to the nature of the attack it does seem like it should; in which case the ability could do reduced crit damage. On hit affects would also work. The ability would have a choice to reduce either movement speed or attack speed, cycling between by clicking R again and would be a point and click ability with a small range. The cooldown would also be high so as to prevent it from being used twice in a single team fight(200/180/160). Being a cut off limb the effects should last quite a while, but they also shouldn't last so long as to be an annoyance to the person debuffed. So I think a good balance is that it is removed upon healing up to full health(or at least back to the health percent they had before they were hit).

I have tried to show this in a way where it is fairly balanced, but since I am not a riot employee I can not say it is in fact balanced, so these numbers can obviously be subject to change if this idea becomes implemented. Tell me what you think.