You could make the quality of the weapon dependant on the type of weapon or enchantment (ie. swordsmanship = better sword, illusion = better enchantment). You can be a little creative for the skill used for each construction. It could also be a percentage chance that the craft or enchantment succeeds.
Having a special place to do it would probably be the best way to go. Like have an forge for weapon crafting where smiths provide you with equipment for a limited time (for a price of course

Anyway, I'm kind of thinking out loud here, let me know what you think
