remove knockdown from all non unbalanced wepons
Eh. Usually the cost of knocking people down is built into the weapon. The Warhammer was the height of hilarity when I was a 1H+shielder -- good damage + knockdown. But right next to it on the list is the Nordic Champion's Sword which is almost twice as long. Or the Long Espada Eslavona which is also almost twice as long and a bit faster (with a really nice pierce damage).
The Warhammer with no knockdown would be kinda useless. Few people use it as it is just because it's so short.
I imagine your REAL complaint is about the "Mace", in particular, aka the archer and xbow sidearm of choice. People don't, I think, pick it for the knockdown -- they pick it because it's the best one slot weapon in the game. 28 blunt! 98 speed! And that's AFTER they nerfed it. It used to be REALLY good.
It's probably still too good, really. I bet almost everyone who uses it would keep using it if you took away the knockdown. It probably is too powerful still for a 1-slot weapon (and a cheap one at that).