Would like to see a new category of crafting focused on the use of levers, cogs and pulley and the like to be able to make new kind of items and structure, among them would be:
levers: that can be used to interact with fixed structure on a distance, for example doors.
Conveyor belt: can be used to move stockpiles, boxes and whatever items is over them from one place to another
Movable walls: walls that can be moved with the use of a lever or some similar contrapcion
Pressure plate: some transparent or invisible way to detect people on certain place (inb4 hearthcraft) and can be detected with a perception vs stealth check
Basic traps: to be used with the preassure plate presented above or a switch: drop boulder over head, the classic log swing, maybe a springed bow.
Ropes: make it posible to tether objects on and make pulleys, also make it so for example a boulder coulbe be teathered to a stake on the ground or the above mentioned preassure plate so it would fall once the stake is removed/tripped over. This is possible because haven have a z axis now.
These are some of my ideas for advanced mechanics butim sure people have their own ideas too