Wow! So cool to see that somebody has implemented the idea I was pushing to my team! I was picturing it as a forge-themed Overcooked game. Unfortunately, we've settled with a different idea.
I agree with the previous commenter: it would be nice to make some manufacturing stages non-blocking and instead time consuming, so you need to multiplex between different activities.
It also would be nice to have different things to manufacture that would involve different steps (although I personally had no idea what other stages could be and even did some research). E.g. Damascus steel would require more iterations on forging, weapons need sharpening, but e.g. armor - doesn't. Also, manufacturing other stuff like horse shoes, hoes (tool) or decorative fences (the later ones e.g. would require making metal rods and then bending them).
Regarding upgrades, my ideas were: the initial oven would require you to use bellows to keep the heat up. Later on an upgrade could be purchased to automatically keep the optimum temperature. Instead of hitting ingots with a hammer, an forging press could be purchased. And so on.
As with Overcooked, a depth to the game could be added by adding multiple characters to control, an awkward shop layouts, requiring passing stuff through tables from different parts of the shop.
And of course, couch coop.
I understand that due to Jam constraints it was impossible to implement all these ideas. Anyways, it is