OK, a book I wrote called
Magesmithing 101 isn't really going to do what you want (and honestly I'm not sure it does everything I wanted it to do) but it does introduce a basic mechanic that i really think applies here: Craft Points.
Essentially the Craft Point system is one in which the complexity of the item, not the price, determines how long it takes to make it. That number replaces the sp value in all craft calculations (so that a copper ring, a silver ring, and a gold ring all take the same amount of time to create).
From there you can build on the system by determining what sort of items you want to allow and how complicated they are to create by establishing a CP value for each. Adding features would increase the CP of the item (not in the book, BTW, as it really is a system for magical items). Some magical propreties would make sense (like Keen for example) but you could also adjust the CP to accomidate things like Balance (giving bonuses to attack), Hardness, and add properties like Heavy, Light, Fortified, etc. for weapons and add features that reduce dexterity penalites, arcane spell failure chances, etc for armor. Steam or Clockwork tech could easily be accomidated with a little effort to establish a standard of complexity and then an increase in CP for various gadgets.
Magical potions (something the book does adress) and other examples of alchemy would simply require certain ingrediants and an appropriate DC set based on CP - the higher the spell level the harder it is to make.
Personally, I wrote Magesmithing 101 trying to replicate a fantasy feel in which Smiths were the only source of magic items and where getting a magic sword was the subject of an extended quest for materials and wealth.
