Here is a list of some items Id like to be put in the game.
Scaffolding: These temporary, stackable structures are basically mobile up/down stairs used by dwarfs for construction. The idea is that they are used like real scaffolding and allow dwarfs to build in normally inaccessible areas.
For example, if you want to make a wall 5 z-levels high, you need to micromanage each level and build floors as needed so a dwarf has a place to stand when making each level of the wall. With scaffolding, you would just place 5 walls on top of each other and the dwarfs would build the first level, then scaffolding next to it, build the next, then extend the scaffolding, and repeat until the 5 level high wall was done. After that, the scaffolding is removed and packed away until it is needed elsewhere.
Bins of Stone: Why can't we make bins and barrels of stone? I can think that someone might believe that a stone bin or barrel would be far to heavy to use and that is why. However, let me point out that you can make them out of metal and metal is FAR heavier then stone. Don't believe me? Here is a Table of common materials with their weight per cubic foot. From this table some stone weights: Granite (168), Slate(168), Dolomite(181). Metal weights: Copper(542), Iron(450), Brass(534), Steel(490).
So a bin made out of Granite would weigh less then half of that made from any other metal. I can't see why barrels and bins can't be made from stone. They are one thing you need plenty of, and stone is one thing you have in abundance. Besides, it could help reconcile the problem with the elves. They hate things made of wood, but even they trade in wooden barrels. Maybe stone barrels and bins might be in big demand because they are 'tree friendly'.
Carts: In effect they simply increase the carrying capacity of dwarfs who can move faster and carry more. These are pretty primitive inventions that dwarfs should have.
Resource Pits: Just the same as pits are now, only you can store wood and stone in them. Since you can't 'bin' stone or logs, pits should allow you to store large quantities in small spaces (taking advantage of the Z space).
Trough: Like a channel, only it is built UP instead of down. Built on the same Z-Level, it provides a path for fluids. It should be accessible (for drinking) on the same Z level it is built on.
Wall Tap: I am not sure if this a good name, but it strikes me that if there is a wall and on the other side of it you know there is water or magma, why do you need to tear down the wall and then build something like a door in its place? A wall tap would be simply installing a small door/ window in an existing wall that can be open and shut via a lever. This way you do not need to tear down the wall first and risk flooding.
Reverse Gear: Not really an item, but a 'mode' you can add to a lever. Only applicable to water pumps now, but it will allow the machine to operate backwoods. This way a single water pump can fill and empty the same room.