I can't believe more people aren't saying BRICKS. Boards should obviously be a high priority one, and then coal. I would like to see salt changed to weight so we can store it in dry goods bags and barrels, also so some recipes can use slightly less or slightly more than 1 chunk or 2. If tea leaves could be measured by weight as well, that would be great. I think the most important ones are
Boards
Bricks
Stones
Ore
For me the hay stack is so badly wrong, a haystack is mass storage IRL but in game it is a frame for drying the hay.
Being able to create large pieces of cloth would be nice, especially if you needed to do so to sell it to the NPC. Perhaps requiring 100 cotton to produce a roll of cloth that we can sell for 150 silver, and small pieces were reduced to 10 silver.