Hi eternalsaga, for this project I started with the default ‘first person shooter’ template which already has a directional light. Having such large meshes was indeed not the most efficient method when working with lightmaps, as some of the floor-meshes are up to 85 meters long. I had to use lightmap resolutions like 2048 to prevent light artifacts.
I did all the unwrapping in 3ds Max with a plugin (SteamRoller) which makes it really easy 
Exporting the meshes with the UE FBX Exporter plugin also saves you a lot of time.