Apart from bugs the biggest issue by far in most games of DF is stone management. After a not-so-small period of time the number of loose boulders in my fort can soar to 10000+. And that does not include stone blocks and ore which is too valuable to dump. So I figured, if we can cut that load on the computer by at least half that should make the game perform a lot better.
One thing I though of was stacking stones and blocks together. The way it works is simple and automated. When you make a stone or block stockpile, stone of the same type can "stack" on the same tile. Boulders can stack up to 4 by placing 3 in a triangle and putting another on top to make a pyramid. Blocks are smaller and can be stacked up to 5 (3 on level 1, 2 on level 2 etc). When you open up the stocks menu, full and partial stacks of boulders count as a single item for tracking purposes.
Now I realize that you can store blocks in bins but I don't like that setup because its hard to get them out again and 10 dwarves carrying ten blocks is 10 times faster than one dwarf lugging a superheavy box.
If this would not affect performance, then it would certainly help us store excess stone. New tiles would be required but they are rather simply to make. 2 stones on the same tile is two lumps beside each other, 3 is a triangle of lumps (like the predators laser sight) and four is 3 lumps in a triangle with a fourth superimposed over the other 3, as if you looked at the stack from above. For blocks the icon is easy, just a pyramid with varying amounts of stones depending on how big the pile is.
Make sense?