Love the game! Very cool, would love to see it go further! Here's my suggestions.
1. A better system for handling multiple customers. Multiple customers right now is a buggy mess and it really dampens the game.
2. Dampen the physics system down. It's really frustrating how often things go flying. They're ingots, not bouncy balls.
3. Change up the progression system. Right now gameplay never changes beyond acquiring the ability to mine things. Right about the point where I started making items from tin I shrugged and turned off the game. Fun for an evening, but a different progression system could be fun for much longer. Consider limiting what you can craft and having expansions based around that. Possible incorporate a quest system with upgrades as rewards. Try to make different metals have different purposes beyond a monetary progression.
4. A better system for transporting items around/mining revamp in general. Mining just isn't fun right now, and the transport system of crates doesn't help. A minecart that you push along a track that does a circle between your smelter a mine might work out well. Bonus points if you can easily send it back to the smelter when you're done. Mining nodes for materials you can't mine shouldn't appear. It's just frustrating. A node should have a number of guaranteed drops of its resource, getting screwed by randomness sucks. 5-10 seems good to me, even if 5-6 appears way more than 9-10. Even 3-5 guaranteed would feel better than the current system.
5. Does Charisma do anything? I like the idea of having a personal progression system as a smith, but I'm not sure I like the current stats. Maybe Miner Mastery, Smith Mastery, and Merchant mastery, giving you more ores from mining, less strikes to craft, more money from sales respectively? Charisma seems a weird stat for a blacksmith.
6. A dedicate button to combine items would be a godsend. Seriously, sometimes merging items together is a massive pain. On that topic a vice for the anvil/workbench that holds items still would be greatly appreciated. Large items are a mess to work with sometimes.
7. A tidy up button would be nice, even if it did a fadein/fadeout and consumed an hour of time. Add in some pidgeonhole shelves and bam, you can actually run a buisness. Drives me crazy that the best way to manage your ingots is to order in bulk, drop the package on the forge and open it.