I like the stockpiles and that they can be limited to selected items be it raw materials, food, weapons, etc. What I would like to see is an ability to also break this down to a ratio or max/goal number.
If I am making a stockpile for raw materials for my carpenter, I probably want the majority of it to be wood with a handful of other materials to be handy for receipts.
It would be nice that once you lay the stockpile and select what items you want stored that I could then state that I want this stockpile to be 90% wood and 5% cloth and 5% stone. This could be very useful to prevent a stockpile from getting overrun with a particular item you need but not in a large amount compared to another.