As this is a manufacturing simulator, geared around effiency, I would like to see the addition of Quality Assurance and Quality Control elements without it turning the game boring.
For QA, the researchable addition of in-line QA stations which can be added like robots would be good, but these would slow down production at each station. This would then be balanced by cutting the time of the main QA final inspection station (by half?) due to the fact you have already checked everything once and this is simply a “pushing pedals and buttons” exercise.
For the QC side, we could have faulty items coming into the factory which could cause accidents and affect your brand awareness. having a researchable QC item to do supplier inspections (so checking items before they enter the factory) would add a bit of cost but would reduce accidents and give a boost to brand awareness. Thinking of Toyota and their airbags for this one.