As we move towards L3 and L4, it becomes more and more important to understand the humans inside the car. Occupant monitoring systems must be able to identify and understand subtle differences in facial expression and architecture, and thus diversity becomes hugely important for machine learning and design. The creation of digital twins can be an invaluable tool for understanding the different occupant needs, facilitating human-centred third spaces that are safe, compliant, and pleasant to spend time in. But how do OEMs  achieve a balance between cost, design, function, and complexity?