Right now, the technology structure is as follows:
Alloy Processing 1 (bronze) → Alloy Processing 2 (electric metal mixing furnace) → ...
↳ Steel Metal Mixing Furnace → ...

But I think something like this makes more sense, and is consistent with the Chemical Processing tree:
Alloy Processing 1 (bronze) → Alloy Processing 2 (steel metal mixing furnace) → Alloy Processing 3 (electric metal mixing furnace) → ...

There are no other unlocks attached to those two techs other than the furnaces, so I don't foresee any complications in the mod by doing this.