I have to make an addition: 40k does have Dwarves in the form of either the Squats or the Demiurg. Torbjorn could be one of those.

Another thing that could work would be a Tau from the Earth Caste, as they are short and stocky compared to their other bretheren and are the ones that build weapons and machines for their military.



Orks could be interesting still: Instead of an autoturret, Torbjorn's sentry could be a small machine gun tower manned by a grot, or even a squig if you feel a bit silly.