Possibility check for my timeline, Noricum

I have a 100 AD POD, which the roman empire breaks apart due to a civil war. Noricum survives and becomes a quite powerful country. However i have a challenge: The Population of Noricum should be rather dark featured like modern Romanians or Hungarians, however retain a celtic language as offical and only language, so it would be a nationstate. Also to get a bettefr view the territory of Noricum is kinda like this: OTL Southern germany + Czech republic, Austria, Slovenia, Switzerland.
 
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