Rather than a whole plugin, could you simply make an event for it?
ex.
What do you want to do at this workbench?
choices
When Disassemble Items,
Select Item, into a variable X
if X == [60] (lets imagine 60 is the ID of your item)
Item 60 (metal machine) -1
Item 61 (metal plates) +4
Item 62 (metal cog) +2
Message:
"You disassemble the metal machine into 4 metal plates and 2 metal cogs."
ELSE (they pick an item that can't be disassembled)
Message:
"That item cannot be broken down."
repeat for other items you want disassembly for
Does something like that work or you need something more elaborate?