I don’t see anything wrong with having the Tinker, but I think if it has a tank spec, it should be a shield-based melee tank (and when I say shields, I mean in the vein of how Disc ‘heals’ with shields and DPS). This shield generator would also be their resource, so they’d constantly charge and spend while making sure they have enough to stay upright after some hits. A Mech Suit wouldn’t be appropriate for full-time wearing, but could work in the same vein as how Paladins get the steed to show up now and again.
Since every class can learn Engineering, every race should be capable of being a Tinker.