If all your lights are being turned on and off in the buildings then having them set to movable would be one option because lightmaps are primarily used for static lighting.
However, here is a use case for using stationary lighting for your objects.
You can setup all your interior lights to be Stationary. This will allow you to toggle the visibility to turn them on and off. Since you are toggling the lights on and off you will only need shadows for when the light is turned on. The shadows can be baked into a lightmap for nice crisp shadows and as your player gets close it will change to dynamic as it’s always done. When the lights are off you won’t see the shadows anyhow since you have the lights off.
I hope this helps.
If you still have questions feel free to ask! 
Tim