It seems like the most significant change is the series of values of that consonant. I don't think the -az in Germanic is significant here because it's a separate inflectional morpheme (and can be ø in the vocative, and in nouns in subsequent Germanic languages).
I'd agree that there's an element of chance in what's happened to the k since it didn't necessarily have to change back to resemble the PIE form, but I'm not sure I see the other changes as ever having moved far from PIE at all.
https://en.wikipedia.org/wiki/Proto-Germanic_grammar#a-stems
I'd agree that there's an element of chance in what's happened to the k since it didn't necessarily have to change back to resemble the PIE form, but I'm not sure I see the other changes as ever having moved far from PIE at all.