It's a hypothetical KK vs boxer fight. A KK guy just has to have enough of a defense to land a few leg kicks to disable a boxer.
Not really sure what you mean but IMO the lack of face punches is a really big criticism against KK. You see top level black belts break down the second they get hit a few times in the face. Once you introduce face punches, surprise surprise it starts looking like KB.
It was such a big problem that the KK orgs considered going back to allowing face punches. But how do you allow face punches while still maintaining bare knuckle? Bare knuckle is the spirit of KK.
I think Kyoukushin matches up well against Muay Thai, because the Thaiboxers offensive hands will not expose the Kyoukushin achilles heal as much. It will be more of a kicking contest, in which I favore the Kyokushin-Kai, since they have more time spent on kicks, given their rule sets.