If you wanted to override the mystery box to force it onto the rooftop, you could edit the _zm_magicbox.gsc file and override the array of chests already in on the map. I've already done the work for it, all you need to do is copy all the code from HERE and compile it as _zm_magicbox.gsc and place it inside your pluto file location t6r/data/maps/mp/zombies/_zm_magicbox.gsc
Shoutout JezuzLizard for all the recompile-able scripts 🙂