I think an interesting change to how stockpiles work is, instead of turning stuff on and off, adding rules.
Normally, what you do now is make a stockpile, turn on "weapons", remove all weapons except for example, warhammer, make sure only "silver" is turned on, and then remove all the qualities except for "standard", if you wanted for example a stockpile that only had standard silver hammers for training.
But what if you also wanted to have the same stockpile accept battle axes and picks of any metal and quality? You'd have to make a second stockpile. Now, this is not such a big deal, but maybe it would be nice to have the option to add several different kinds of items in the same category.
In the proposed system, you "add" a rule, and it goes into some list. For instance, you add a rule that says "category: weapons, items: battle axes and picks, metal: all, quality: all", then add a second rule that says "category: weapons, items: warhammer, metal: silver, quality: standard". The selection screen would be pretty much the same as the current stockpile screen, except that you can't activate multiple categories.
An option to allow mixing items from different rules in the same bins could be helpful too, but that's another matter.
Opinions? In a way, this would be like having overlapping stockpiles.