Just to clarify, you're saying the person that presses kick when he registers the startup frames of the enemy player's kick, knocks the other player down? So the 2nd player who pressed the kick button benefits? That would seem correct. However, did you test if it works regardless if you hit the other player with the kick or not? Or is it more like a counter-throw press in a fighting game, where you wouldnt have to even hit the other player directly with the kick? Is it as long as the feet touch (lol @ "it's not gay" innuendos), or does the kick have to actually hit the other player's body as well? If you just have to press the button without hitting the other player with the kick, I think it would lead to killing kick completely.
Also I am of the opinion that kicks don't need to be changed at all. I can hover out of kick range for the duration of a duel, not seeing how getting kicked isn't the player's fault in the first place. And if you have a point blank short weapon, that's the whole point, you take on that aspect of the weapon's weakness. People who spam kick get hit, they can't turn with you and they can't block thrusts. I'm pretty sure shields block frontal side attacks and overheads. It just reduces the side coverage of the shield during the kick animation, so you can sneak in attacks around the shield since they can't turn with you. I could be wrong, shielder's don't kick very often, they just fiercely hold right click. But I do remember hitting the shield after a shielder threw out a random kick while cornered. God forbid the only thing that can open up a right clicked shield(kick), actually gets used on them.
EDIT: It's not like every peasant out there is kicking people like a pro, how often do you see a good kick executed on battle? When I started getting kicked by top players a long time ago, I realized that I was "W" warrioring way too hard and modified my playstyle to lessen the chance of being kicked. As long as you're concious of it in the fight it's not that big of a deal. I didn't cry nerf this, nerf that on the forums, I found a way to deal with it, just like I dealt with numerous nerfs to my build.