One thing that can add diversity to the synthesis mechanism would be ingredient items that can add bonuses to an otherwise basic recipe. For example, instead of just increasing quality, why not take a normal recipe - a Canvas Doublet, for example - and keep an extra slot available for a series of "bonus" ingredients, that when added, can offer small bonuses to the item. Such as, additional point(s) to defense or evasion, or a modifier to base states like Dexterity.

With this system, people can make all kinds of Canvas Doublets, not just ones with different colors. It has the benefit of offering variations to the kind of items available for trade. Instead of just having "quality" be the only variable for an item, there could be many, and it would be exciting for players to try to find these bonus ingredients (maybe they are only dropped by NM's, so that they are rare), and use them to make many items that carry a certain uniqueness to them.

Comments?