Hi! Yes there is something can be done. Level Cache folder contains all the level data - thats correct but they connected to GM campaign via GMScenes.lsf file where the connection established. If you decide to work together on GM campaign be sure to have that file correct - because if you both creating new levels - you will need to merge the files on your own.
It works pretty same way for vignettes and overview maps. So if you added new vignette (i'm not talking about images) - it will be registered in Vignettes.lsf file so you friend will need to have record in his file as well to see it.
To ease your flow i would recommend to divide work between you guys in following fashion:
"One doing narrative and other doing levels". This way you could just send whole files to each other without messing with manual merging.
