Hello fragfest2012, and gerbilho,
Your logic is sound. This is a recommended workflow for using both indoor and outdoor lighting. Note : There is currently a bug with static lighting and foliage. Foliage painted past say 400-500 instance static meshes will derive it’s light source from only one light source. It is recommended to use dynamic lighting for your foliage, as with large foliage scenes, dynamic lighting can provide better performance as it will be a smaller calculation than that of your lighting cache. You could limit your static lighting to your indoor areas where the lights attenuation radius does not influence any of your instance static meshes.