If you’re going to open the can of worms to allow it multiple classes.
Dragons at their core are elemental species (before the titan magics; that’s how they were depicted not from bronze,blue,red or yellow but by being an Stonescale,Stormscale, Firescale and etc.)
Giving dracthyr’s the option to lean towards the more natural version of Dragonkind is not only lore friendly but just the correct thing to do.
They could even claim they are Dracthyr under employment of the teachings of Vyranoth.
The only counterpoint i can think to not allow them shamans is the argument that they were created to use the magic of the Dragonflights, to be Evokers… but these Dracthyr aren’t Evokers. they didnt cook in their test tube long enough, Give them shamans.
One of the Dragon Aspects is quiet literally Aspect of the Storms.