I am not a Vintage player, but follow the format nonetheless.
I've always loved Goblin Welder in Legacy and Casual, mostly in a prison/control shell, and I am currently experimenting with it again, due to the release of the recent sets which had some Welder toys.
Maybe a some food for thought for you:
Wishclaw Talisman has been pretty amazing with Welder. Activate it, in response weld it out, tutor.
Also works with Engineer, but maybe needs more support (like bouncing).
Witching Well is worth considering, too. Taps for Tangle Wire, activates Mox Opal (less important for you) and smooths your draws, sacrifices itself to activate Welder, and draw engine in the late game with Welder.
Emry, Lurker of the Loch: Obviously plays nice with Welder, helps for Barbarian Ring (threshold) and also good if you play Crucible (finds Wasteland). I am undecided if it's better than Engineer, though.
Lesser Masticore is not bad, too. Feeds Welder, and persist is nice with Smokestack. Turn 1 Welder, turn 2 Mastistcore, discard and weld <3. Even if it's only a Smokestack, it's a nice tempo play.
However, its ping ability is too expensive most often.
I also tried Mystic Forge, but I think it's better in a pure combo deck.
Due to the black, blue and red color requirements I am trying these cards in similar shells, like the old 5c Stax shells of yore.