Now that you mention it, there are some additional features that I would really like to have in this game system.
In fact, I don't think we've committed to a particular problem statement at all.
The first is choice between inputs.
Perhaps this requirement could be fulfilled by just adding more processes, I don't know.
On second thought, I think I will implement this as separate processes, but give the designer some shorthand tags to make it easier for him to make alternative processes.
The second is a quality level computed on each item. Each process would contain a formula that calculated the value of properties on its output(s), from the properties of its inputs.
The optimizer would then try to optimize for speed, quality, or a balance between the two.