One can only hope that a few other ice types get Freeze Skin. Its a great ability in theory, but probably won't be very useful on Amarusu. Generally speaking most fossil Pokemon are slow, with a few exceptions like Kabutops and Archeops, so if Amarusu follows the slow trend, I can't imagine him living long enough to do much damage in the higher tiers.
Imagine how deadly something like a Mega-Weavile getting this ability. Using return would give you a stab 102 BP Ice move, allowing Weavile to be able to actually dish out some damage.
Its a shame the type chart didn't make Ice any better of a typing defensively speaking, but maybe this new ability, if distributed in an optimal manner, can at least buff a few Ice Pokemon.