...Just kidding! I know the goal is to prevent playing with offshore oil and oil rigs. Since 2.1, the Oil Rig is separated into its own mod. You can simple add "!cargo-ships-oil-rig" to the dependency list. You can remove
if mods["cargo-ships"] then
seablock.lib.hide_item("oil_rig")
end
from unobtainable-items.lua