First of all, my apologies for slow replies. I caught the 'con crud' at Gen Con, so I avoided doing much of anything the past 2 days so I could catch up on sleep and healthy food.
But, on to the question!
While the first rule of any campaign is that the people playing in it can change whatever they want if it makes things more fun for them, there is a distinct mix of magic and technology that we're shooting for with ZEITGEIST. We want to generally follow the way technology developed in the real industrial revolution, but let magic spice things up occasionally. Some wondrous and awesome things will show up in the course of the PCs' adventures, but you shouldn't assume these things are 'normal' in context of the rest of the world.
Magic doesn't have to follow the same rules as science, but it has its own set of rules. Gold blocks teleportation. Different planes in the night sky influence the efficacy of spells. And it's possible to infuse an elemental into an inanimate object in order to make a golem. But magic ultimately requires power sources that are finite and somewhat finicky, and which usually require either intense study or mystical blessings in order to wield.
It's just not feasible to make an assembly line to produce magic swords, because the fabric of magic itself resists standardization. It's intensely personal, and the best you can do if you want a lot of it is to start a cult and teach a bunch of people the same chanting and way of thinking.
Technology and industry, though, are inventions that just need to be explained and learned; you don't need an emotional connection to a gun in order to know how to build one. Twenty steam engines can be built with the same source of iron, but if you wanted a magical energy source to propel a ship, you'd need to craft each iteration individually.
Now, it is possible to combine science and magic. But the style is not "assembly line of golems." It's more like "+1 locomotive." You don't make a lot of mild magic things; you make a lot of technological things, and occasionally someone invests the extra effort and resources to enchant it.
The exception to this is 'alchemical items.' Stuff like firedust and alkahest (universal solvent; i.e., acid, which crops up in adventure) just require a spellcaster to fiddle with raw materials to create them. Anything that's one-use gets a waiver, mostly because we didn't want to use gunpowder.
So basically, feel free to have whatever weird steampunk stuff you want, but remember that anything with magic in it is not going to be mass produced.
(At least not early on in the campaign.)
