At present, crafting skills has two positive effects: the chances of creating an object of higher quality increase, and the time it takes to create objects decreases. However, there are subtle drawbacks and disadvantages to these effects. Sometimes it is desirable to have base-quality objects, especially in things that are intended to serve basic roles. Producing nothing but exceptional and masterpiece stone doors is a disadvantage if you're trying to create cheap and spartan bedrooms, for example. You can always assign an inexperienced worker to the task of creating basic goods, but they eventually gain skill. Skilled engravers produce historical documentation in a manner that is valuable both to the dwarves and to the player, but sometimes we might wish them to produce the simple designs they once made - and this is not likely with a skilled engraver. In this way, basic goods are a limited resource of sorts.
I also find it a bit strange that the time taken to create an object is inversely related to the probable quality of the object. Skilled workers should be able to create higher quality items faster than less-skilled, certainly, but I feel there should be more of a trade-off between speed of production and potential quality. As the saying goes: Fast, Cheap, Good: choose any two." The 'cost' of production is constant in DF, so we're left with two options - we should have to choose between them.
Therefore, I make the following proposal: at some level of implementation, there should be a slider control that operates along the scale of Quality to Speed; the setting would determine which desirable property was prioritized. Worker experience would determine how much 'skill resource' is available to be alloted to the priority. This has a variety of desirable effects.
An unskilled worker couldn't choose to go faster at the expense of quality, nor could he choose to sacrifice quality for speed. The goods are made as well as he knows how, and no amount of extra time can improve them; they're made as quickly as he knows how, and they cannot be made any more crudely without ceasing to be functional at all.
A skilled worker, however, has options. Because of his greater skill, he can make better objects, faster. If he chooses, he can rush the work, churning out goods at an even greater speed at the cost of limiting their quality. Or he can take additional time beyond his base rate, using the extra care and effort to produce goods of higher quality than his normal work.
A Legendary crafter could produce basic goods blindly quickly, compared to an unskilled worker. Or he could take more time and aim for great accomplishment; the greater the potential quality of the result, the more time would be needed. The default setting would allot skill resource equally between skill and time, resulting in skilled workers making better goods faster than unskilled - but not as quickly as they might, and not well-crafted as they could possibly manage.
I am uncertain as to whether this slider would be best implemented on individual dwarves, individual workshops, or as a property of individual tasks. I suspect that setting this quality on a workshop would be easiest to implement; assigning workshops to individual dwarves is already a feature, so a skilled worker will probably have his own tools and raw materials that are denied to lessers.
Thoughts? Suggestions? Criticisms? Please share them.