As for a Crit Hit Kick Based WS, why would you even want this. To optimize it you would have to use Footwork, which is so much slower than meleeing regularly.
There is something called a Footwork Build.
Using Ursine +1 or +2 you can kick twice almost ever time. In abyssea, these kicks can crit for 350-500ish points of dmg. 2 kicks gives you 25 TP, and WSing when you have footwork active gives a large amount of TP return (46tp return for Asuran). On top of that, Footwork gives you an attack boost of 15% with AF3+2 feet which also increases the weapon dmg while using WS by +45 which is added to the +18 that footwork naturally gives making a 53 dmg weapon. Just because footwork attacks slower does not mean it has no use.