Good question, but this was an issue I quite fast figured that its better to not rotate the planet. There is 1000s of dynamically made objects on it, 100s of skeletal meshes following different splines, and even 10s of different levels made for spawning foliage under different conditions. Rotating foliage etc. real time is really not an option, when the desired visual effect of day/night can be accomplished with just simple light rotation. Which, is not thaaaat simple after all, but still more manageable.
I can get it lit naturally with 1 light in this approach as well. The different lights are just for atmoshphere, colouring the evening/morning parts to be visually more intresting than 1 simple sunlight with ambient for night would do. I also have the cities lighted up during night via dynamical material changes to emission maps and point lights, but thats an different thing and doesnt really change here.