There's been a lot of QQ about this already. Blizzard has had 3 versions of the lightning saber worg since wotlk with the only one released being Skoll. Now even before I tamed mine, I thought "Damn those other models look sexy!", indeed they still do.
However not only is one of the new models being introduced, but its being made into a common pet that is available to all hunters. The thing that was unique about BM was the fact that they had the ability to tame very unique pets.
When you were SV or MM you did the same but with pets that were available to that spec, pets such as Sambas, Rak'shiri, Skarr, Karkin or even Rattlebore and so on.
With introducing these Thundermaw you're making BM that little bit less special, and believe me, after grinding for so long getting all of mine, it feels like a kick a kick in the nuts to know that not only the hard work getting Skoll but also the fact you've reduced a model widely regarded as unique even as a re-skin to a common level.
Things should really be addressed and IMO you have a few options to take:
1. Make Thundermaw untamable.
2. " and introduce a new rare pet which has the same skin which is available to BM only.
3. Make Thundermaw untamable and as a compromise introduce a new rare pet that all can tame, this way Skoll is rare and unique, the new model is rare and unique, and people actually appreciate the time and effort spent in getting this pet, as well as restoring hunters faith in blizzard not !@#$ting all over them.
My personal preference would be 2. simply because BM needs to be maintained as the unique spec with having their own specs pets (which begs the question why make a pet unique to BM common anyway... nvm), thats just their thing.
The best way to keep people happy would be the compromise, I can see why you did it, trying to give other specs a cool pet but... there's still so many out there that you don't even need to be BM to obtain.