I have no clue if Criss will be able to do the part justice and for the most part, this is just me playing devil's advocate, but if 15+ years ago, you had only experienced JCM in his prior musical theatre roles, I daresay no one would have thought he had a voice suitable for the kind of music Hedwig sings either.
Also, at the risk of heresy, JCM in fact DOESN'T have a particularly "strong rock voice". He has fantastic rock instincts and magnificent interpretive skills, but the instrument itself is not particularly strong -- especially in this go-around -- nor can he really conjure whatever rock "edge" he may have previously been able to offer. The brilliance in this return to the role is that it doesn't matter.
In any case, whatever Criss does, I don't doubt that he will pale in comparison to JCM, but hey, nearly everyone does in this role. Suggesting that Criss's voice isn't well-suited to the part, though, doesn't really fly with me until we can hear how he actually sounds in it.
"No matter how much you want the part, never let 'em see you sweat." -- Old Dry Idea commercial