Lord_Shonus: Basically, I'm not happy with it at a specific level, but fine with it on a general level.
Losing the ability to cast bronze puts you in utter stone age tech. The only thing above that is steel right now. So it's basically just making "technology" about whether you have steel or not.
In order to make this make sense, you'd need to start putting in various levels of tech - "Crude Steel" (possibly worse than bronze), "Wootz Steel", "True/Dwarven Steel", and maybe a "Meteoric/
Thunderbolt Iron" that can be mined out of small deposits of meteor on the map. These being progressions along the path to making a better steel, which make the previous versions obsolete and replaced.
As for the rest of the game, however... I'm generally opposed to the notion of actually barring any of the things we have right now from being made. (Sorry, your civ hasn't researched beds yet, now sleep in the mud!) This means that either we need progressive levels of finished product (and how do you make a better table, really? Does it give you a +20% upgrade to its levelness?) which only makes sense when we are talking about, say, types of armor, where we could have players start with scale mail or banded mail and only make field plate armor that can totally cover the body at the higher tech levels, or if we are talking about tools/workshop upgrades or finished products and trade goods that can be cut on or off.
Workshop upgrades: This requires a revision of the entire production cycle to even start being viable, as production is largely a matter of moving from the stockpile to the workshop and back, not the time it takes to make something. I DO, however, like the idea of having "Ad hoc" workshops that hurt overall item quality, with the ability to make better tools for completing the job, which give you better quality workshops that make better quality products... but quality is a minor concern in this game right now.
Andeerz: It's going to take a major set of changes to the game, not just FPS, but plenty more late-game challenges to keep the game interesting beyond the challenge of self-sustainance to make that sort of generational thing work... you might want to get on some threads for creating late-game challenges, and advocating for or inventing some ways to keep the player occupied. (Empire mode? The player stays in his fort, running it mostly on auto-pilot while planning to take over the world?)