I have a model with a number of LEDs that are lit depending on the external situation (alarm, reload etc.).
The is a variable designating which sector of a LEDs circle is lit. Say, for the red circle, 0 means all LEDs are off, 3 - the half and 7 - the full circle is lit.
The first thing that comes to my mind is creating a separate channel for each state for the emissive component of the material, but it would be a waste of memory (24 channels total). That is the only idea that comes to my new-to-UE4 mind.