I never did a lot of smithing in ADOM. For one thing, collecting ore and the act of smithing took a lot of time, unless you were an actual weaponsmith, and I always like to beat ADOM before day 65 or so. If you weren't lucky enough to find a forge in the UD or have Dwarftown spawn before D:10, smithing would also involve a bit of corruption, which I'm never a fan of. Finally, I never saw the point of wasting so much time doing something that a blessed scroll of defense or protection could do just as well.
Time constraints and finding corruption free forges won't be a problem in JADE, which addresses two of my issues right off the bat. The last issue is making smithing more interesting than a scroll of protection. Here's a few of my thoughts, and I've love to see yours.
The Smith Guild
I think Guild's are the coolest thing ever, as you might have seen in my mindcrafting thread, and I hope there's a guild to be found for every possible profession. There's absolutely no way the game could exclude a smithing guild.
For a fee, the guild would teach the PC how to smith, and for another fee one could have access to a force and smithing equipment like anvils and leather aprons when needed. But for a character interested in doing more, advanced smithing techniques could be taught as well.
A character with a high level in both smithing and gemology should be able to learn the art of affixing precious gems to the pommel of weapons or perhaps in armor as well. When encrusting a normal gem like a sapphire or ruby into an item it could raise its sale value, making this a lucrative way to make money. Armor embedded with gems could also raise the character's appearance (and perhaps make him more likely to be robbed).
This gets interesting when you begin to encrust magic gems. A gem of fire could add fire damage to a weapon, while a crystal of learning in a helmet could transform it into a helm of mental stability. There are few types of magical gems currently in ADOM, so you can add loads more to allow for different magical effects and modifiers.
For balance issues, there should of course be a cap on how many gems can be encrusted onto an item. It should also probably be impossible to add magical gems to an artifact since the power of the object is too strong to be enhanced by a piddly gem.
Artifact gems that could add multiple modifiers when embedded in a weapon could also be a possibility.
This is the main reason I would say for joining the smithing guild: they would teach a character how to create his own weapons. For balance issues, this should be a skill reserved for very experienced smiths. The first step would be learning how to create a basic item class, such as an ordinary polearm or a helm.
The second step could be learning how to forge weapons from rarer ore like adamantium.
The final level of item creation should be making your own magical items. This would best function like a more complex version of alchemy in ADOM. Each item "recipe" if you will would be based on variables like ore required, smithing skill, items such as herbs, gems, and monster body parts, and other skills like gemology and even magic.
For example, a simple recipe like a sword of speed could require mithril ore or better, smithing of 75, and the bones of a quickling. A really nifty item like a mace of devastation could require eternium, smithing at 100, magic at 80, demon daises, the skull of a swamp hydra, and the powdered bones of a black dragon. Or something like that.
Liek alchemy, the recipes could be randomly generated. So the smithing recipe for a sword of speed would always be relatively simple, but constantly different so that you could never plan too far ahead to get the desired weapon.
Different smithing guilds could of course offer different skills and recipes to learn. A chaotic smithing guild could teach you how to make vampiric weapons for example, which would require in addition to anything else proficiency in Necromancy.
Smithing and Artifacts
I personally don't think you should be able to modify, let only create, artifacts, but perhaps others have ideas for implementing this in a balanced way.
Any thoughts or item recipes you'd like to suggest?