Personally, I do think that various smithing skills are far too rewarding when compared to other economies, considering how simple it is to set up. And I almost feel like it would make sense to have a ton of skills for metal, since... they're dwarves. At least 50% of them should have metal-related skills, right? 
Realism is great and should be considered, but game fun and balance should probably take precedence. Right now, (and maybe changes to this are already in the works) I think the Farming and Metal industries are way too easy and profitable (not to mention aiding the dwarves in survival a lot more) when compared to other industries like Meat, Glass, and Wood.
So, I could see more complications to smithing helping to make other industries more attractive - at least in early fortress life.
Wait, what?
Right now, the textile mill is probably the most complex industry, but metalsmithing comes close.
Also, metal is too easy to make money compared to things like glass or wood or meat?
OK, if you have magma and sand, and simply channel that magma near the sand, and you have what effectively amounts to a limitless license to mint money. You have infinite green glass, which can be set up to provide infinite glass items, which are at least decently valuable, or you can make raw green glass and decorate everything else. Then you can make clear glass if you have ashes. Yeah, maybe it's labor intensive, but you can easily outpace a handful of platinum items with a 40 material value by simply making over 20 glass items. And those glassmakers would rise in experience faster, as well.
Which brings us to wood. Yeah, sure, it's not valuable, but it doesn't really have to be - you generally use it for beds, barrels, bins, and the charcoal or ashes that are used for other industries. Without magma, that metal industry requires a wood industry. Even with magma, you probably want wood for steel production.
Stone? Stone is basically the same as glass, you have more stone than you can do anything with, so you might as well turn them all into doors or blocks or tables or something.
Meat? Yeah, not as powerful or valuable as farms (unless you go unicorn or mermaid breeding), and it has some more micromanagement involved with ensuring you have enough butchers on duty, places to put the chunks, or manually designating the victims. Still, you do get food, bones, and fat all at once.
Really, I hardly use my metal production at all. I pretty much make steel armor and weapons, plus silver weapons, and maybe make an alloy of tin and copper (depending on the relative amounts available) to make chains. My glass production is just so much easier for trade goods, and I don't have to worry about running out of sand.