I'm writing this before doing a proper playthrough with the mod, so I'm not 100% sure what the theme is.
But looking at the tech tree, the new machines and the new production chains for this planet I think the Advanced Assembling Machine from Age of Production fits as a reward, as a parallel of the Electrochemical plant. It is a generic reward but having it as a T3 / Aquilo level planet reward makes sense and that will give electric coil / galvanized steel more uses. The only problem is the Mechanical plant being too similar, maybe you can make it as only the Mechanical plant can craft this advanced assembling (+ the lower level assemblies) and remove the base productivity of the advanced assembling.
