1.This is more of your opinion. Just because you don't view Tinkers as deep or as interesting as DRs or Necromancers doesn't mean that they aren't deep and interesting to other people.
2.Blizzard has already inserted the Tinker concept into a medieval fantasy world. In addition, if you feel that a Gnome or a Goblin driving a robot suit is out of place, you must despise Draenei and the Legion riding in on space ships, or anything to do with the Titans and their technology. Also, the Tinker concept is not based on the professions, it's based on the Tinker hero from WC3 and HotS like the other expansion classes.
3.That's true, but that only makes the class more viable because Goblins and Gnomes are playable races who are missing a vital part of their racial lore (piloting mechs to compensate for their lack of physical strength).
4. They're also used for shooting demons in the face:
5.This is just more of your personal opinion. I appreciate you sharing it, but that's really all it is.
6. Which is why it will never be a part of the professions. Professions have to be balanced just like classes, and a profession that allows you to mow people down in a robot suit would be grossly imbalanced and make everyone spec into it over the other professions. This is why Engineering and Alchemy's main purpose is to craft trinkets for people to sell.
7. Both professions would be enhanced, since it would give another class for them to sell items to. Engineering would definitely get a boost since Tinker players would no doubt take up the Engineering profession for more immersion. Hell, Blizzard could even give Tinker players a bonus in Engineering just to sweeten the pot. Professions and Classes don't compete with each other, so the notion that a
class entering the game based on technology would harm a technology based
profession is complete nonsense.