Here's a mod proposal:

You can only smith items that you have actually found in the game world, as well as having the necessary skill/perks. Probably, you would have to smelt the item down to gain the recipe, which corresponds nicely with the existing enchantment system. This adds an extra incentive to exploration and nerfs the overpowered and cluttered smithing system in an immersive way.

http://skyrim.nexusmods.com/mods/19416/? edition does this by adding a script to individual items, which means that it does not apply to equipment added by third-party mods (JaySuS, Immersive Weapons, etc), rendering it somewhat redundant for a heavily-modded game like mine. http://skyrim.nexusmods.com/mods/9959/? also serves a similar end, but I'm not sold on the whole recipe-books thing, and again will only apply to vanilla and supported mods. I feel that it should be possible to run this check universally for all smithable items, but I'm not sure what the best way to go about it would be - haven't used the CK since Morrowind days!

Any suggestions/feedback would be much appreciated