This is how I would have made the tweakables optional

This adds a Settings button to the build engineer, adds settings to toggle each of the tweakable items, fixes the settings so they are always all present and in a consistent order (and the layout is easier to control in the code) and fix the Log Sim from throwing an exception due to a missed part cost int/float change.

I thought about putting sliders into the settings window but then you couldn't see the effect of dragging them on the calculations (and this way was a lot simpler).