a) see Hebrew and further see Latin as official languages in Croatia and Poland
b) see Israel and basicly every colony
c) now this made me curious how did the Yugoslav identity harm Yugoslavia and they maybe in theory gave it up post 1945 but still introduced Serbo-Croatian and introduced Yugoslav as a nationality for those not wishing to chose one of the other official nationalities
Hebrew and Israel are totaly wrong examples here.
Colonies and Latin too.
Because nationalists on all sides saw introducing any Yugoslav identity by the Government as destroying of their nation, and neither Yugoslavian nation did not want that. So, naturally, they will resist the country/Government who tries to do that.
And one of the founding myths of second Yugoslavia was that they will be better than first Yugoslavia in solving of "National question" in Yugoslavia- that means to give each nation in Yugoslavia equal opportunity to develop his own national identity.
Serbo-Croatian is one thing ( because two/three-four today ) languages are very similar, but nobody tried to include Slovene or Macedonian language there. And even that died-off after 1974. About Yugoslavian nationality, yes, they have allowed to declare itself as Yugoslav, but nobody forced you to do that, if you wanted to do that, you could, but nobody forced you. And that was mostly the choice for those from mixed marriages ( mostly in B-H ) and Communists ( local version of communist internationalism ).