Its absolutely physically possible to do it with consistant training. I don't question whether or not a lot of the power would be lost. High speed means less power.
Look at the difference between a Muay Thai roundhouse and a Karate roundhouse. In the Thai roundhouse, there's a prepartory motion that aligns the hips accordingly and a powerful rotational strike, in the Karate style there is no prepatory motion, the hips, feet, truck, all rotate as one. This motion(Karate style) snaps the kick almost 25% faster than the Thai style. However the Thai style roundhouse hit with almost 20% more power than the Karate style. It should also be noted one strike was with the shin(Thai), the other the instep(Karate), which also limits power. This was on an episide if MMA Live on ESPN 2 just before Machida vs Rua 2, I can't find the damn vid on Youtube though!
For me repitition drills have always been about endurance more than power. Not to say I don't use repition to develop power, its just more of a low deliberate repitition to understand balance, momentum, body mechanics, etc. and a rapid snap of each individual kick.
Honestly, there's only two situations where fast is too fast, this being where the kick is thrown with such vigor and speed that balance is compromised. Because if you lose balance, as I'm sure you know, you lose almost all power. The other being that you're kicking too fast too repetedly too often without proper recovery, which can damage muscle tissues, tendons, ligaments and bones. But the second situation is more of a rarity that can only be developed over a long period of time.
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My goal is to end my opponent --Carlos Condit