Personally I don't think layback spin would be the best option for Yuzu, or for almost all other male skaters for that matter. The basic layback shouldn't really be terribly hard for most ladies, because they are naturally flexible in the lower back, but it's another story for men (hard proof is lack of men doing them decently in competition Adam's layback as part of a combo is nice enough but I'm not a fan of it either, really).
Yuzuru is of course one of the more flexible male skaters, but I in my opinion, not enough flexible in the back for a (good) layback. If I have to be honest his Biellmann isn't one of my favourites spin positions of his either, but it's amazing in itself that he can do it. Still think his real strenghts lay somewhere else, but hey, just personal opinion If he wants to work on it, then I hope he will prove me wrong and show the most beautiful layback, either way I still will enjoy it because it's Yuzu. I don't think it's really wort it though...