More d20 damage

I have spent several posts considering making a single roll for attack and damage, and even more posts considering Critical Hits.

But what if we combine both?

Here's what I am thinking: if you beat AC by 10 or more, you deal maximum damage.

But if you beat AC by 11 or more, you add the excess damage (e.g., +4 damage at if you beat AC by 14 and so on).

Beating AC by 10 or more is something that RARELY comes up, EXCEPT for strong fighters against weak/unarmored foes.

So Conan could maybe defeat a horse with a single punch - although it is unlikely. 

(Or defeat a sorcerer with a chair, if you want an example from the books).

But your average magic-user is unlikely to get much out of this (on the contrary, if he has no armor, this puts him in more danger!)

What if you get a natural 20? I dunno, maybe you get maximum damage regardless of margin, or double damage, or add five points to damage, or count it as 25, etc.

Effects:

- Fighters get stronger.

- A thief's sneak attack gets better.

- Big monsters get scarier.

- Combat get deadlier and less predictable.

I like them all.

Maybe something else I'm missing? Let me know, Anyway, just a random thought for now.