There's something to be said for trying unconventional things. At the very least, it creates references that can later be called upon when building other decks. Also, Welder, when active, can be a beating.
One of Welder's weaknesses is Jace, the Mind Sculptor. He doesn't like how Jace can interact with him, often times negating a board state that took a couple of turns to set up. Jace, it seems, is at an all time low in terms of play since his printing. This is a mark in Welder's favor.
The issue with Welder at the moment isn't his power level (his effect is still quite good), it's that he never seems to be able to stick around long enough to get going. At any given event, the following cards see a fair amount of play:
Swords to Plowshares
Mental Misstep
Dismember
Lightning Bolt
Abrupt Decay
There's more removal out there (in the form of counters and kill), but that's a decent rough approximation.
If we're going to play Welder nowadays, I think we need to do two things:
1. Negate any of those cards to the best of our ability.
2. Be built in such a way as to minimize the impact of those cards.
The first point leads me to want Cavern of Souls in lieu of basic Mountain, as it potentially shuts off Mental Misstep.
The second point is more a commentary on the mana base and the choice of threats.
MUD Marinara was the last successful Welder based Shop deck that I can think of. I'd want to consider looking at that list for a rough approximation of where to start.
Your list occupies two spaces; on the one hand it plays many creatures that are best suited to aggressive style decks. On the other hand, it has control elements of a traditional Shop prison deck. I think that you're probably going to have to commit more towards being one variant or the other.
I'd call what we're seeing the renaissance of creature based strategies for Vintage, but that's probably a misnomer, as I don't think that they've ever been this good before, or had so many viable weapons to combat the metagame.
I think that may lead towards an interesting strategy. I think it's possible to build a new style of control deck, where in lieu of trying to establish a backbreaking Smokestack, you look to establish control off the backs of the various bots that combat opposing creatures so well. Sundering Titan, Steel Hellkite and Wurmcoil Engine are great trumps to Delvers, Deathrite Shamans and the assorted small beaters of the field. The irony in wanting to do this isn't lost on me, as the sacrifices to the mana base required to run Welder make casting any of those cards more difficult than they would be in a traditional MUD style deck.
I don't think that there is a modern Shop list that can be built nowadays without Lodestone Golem. Lodestone Golem puts a tremendous amount of pressure on colored spells. As such, I'd want to ensure that if I was running colored spells that they'd be so powerful that they're still worth trying to resolve through my own Lodestones. Welder falls in this category.
I think Magus of the Moon and Null Rod are similar cards in that they both look to 'Time Walk' an opponent for a few turns before said opponent is more likely to break out of the forms of control that they exert. Magus, being a 2/2, gives an opponent a long time to get out from underneath his ability, and, on top of that, Magus will also shut off our Shops, Tombs, etc. I don't think Magus is worth playing through Lodestone. I could be wrong.
As far as cards like Eidolon of the Great Revel and Solemn Simulacrum go, I don't think they have a place. If we're cutting the Mountains for Caverns, there's no benefit from Jens' searching ability. Eidolon just seems like a tough card to cast in the prior incarnation of this deck. Additionally, as much as I'd love to run Factories, I don't think we can run Factories while still running the other lands that we need to in order to reliably cast our threats.
If I was going to play a Welder based Shop deck, I'd start with this and make some changes:
http://www.mtgdecks.net/decks/view/19157I'd immediately cut:
3x Phyrexian Metamorph
2x Karn, Silver Golem
I'd consider running four Spheres in lieu of four Thorns, leaving us with a 4/2 split.
I'd add the fourth Smokestack.
I'd add four Phyrexian Revokers.
I'd consider cutting the Barbarian Ring for another utility land. Maybe Karakas for Oath, or something else, so long as it taps for mana.
Finally, I'd want to find a way to run the Razormane Masticores in the main. They're an absolute beating against just about all of the field right now, and because of Welder shenanigans, in combination with Welder, they're capable of killing Trygons. 5/5's with first strike are a serious problem for the field right now.
The problem with this style deck is that you're going to be a dog to Oath, nearly regardless of your hate. I'd pack the board with three Duplicant and then see where that led me.
I may follow up on these ideas and take this style deck to a tournament sometime soon. If I do, I may follow up and let you know what worked, what didn't, and what it should look like moving forward.