Light Fakery

One method I have explored for reducing the number of lights in a scene is the use of emissive materials.

Lift car interior

The lift car is contained within semi-opaque walls. Lighting from behind using, for example, four area lights and transmissive materials could lead to hugely increased render times.

This solution uses one point light and the walls have a subtle glow. While it may not be physically accurate, it does give a pleasing result.