I think it's probably unnecessary for Kazuya to be baptized. He doesn't need an implanted stigma to accomplish the Ereinbar Set, we've already seen that (and with multiple partners at that). In fact he can actually control his partners' actions to some degree, which is more than any other Limiter has ever been able to do.
The Freezing ability still has the same value it's ever had; it's just that at the current power levels being tossed around in this arc it is being easily overridden. We've been told that Freezing is not simply a power to "freeze" a target's movements; it also enables telepathic communication with the target. I think that's what Freezing actually is: telepathically overriding the target's control over their physical actions. A sufficiently powerful mind can override that control.