Shaori,
that's just a great idea - I haven't though about it until yet and yes it's a kind of obvious anyway.
Well... what to said about it, it stands by itself:
First, it could be seen as a "machine healer" for catapults-like units for example or as a "stonecutter" for the TumbleStone "health".
Second, it could be upgraded as a crafter/blacksmith, for items and gears (like the hand-grenade of the coming update 5

).. crafted with the materials we shall procure him.
And finally, it could be upgraded as a defense architect - of course.
Well, tell me Shaori, which title want you? something like
King's Blacksmith?
Well, I'm going back to my Game of Thrones serial