Well, I've noticed that you can have a few wld files at a time....so I was wondering, is it posssible to have multiple 'worlds' in a single map? So using Zerted's custom game modes, load say three worlds using different modes? My reason behind wanting to do this is having three maps set on the same planet (and all using 90% the same props) without making it into a humungus amount to download...

You can load layers from other maps into your own map, if thats what you're asking... Just add another ReadDataFile() in your lua where it loads your main map/layer configuration.

Pretty sure that won't matter - the world .lvl files each duplicate the objects when they're munged - you can't have ABC1.lvl borrowing objects from ABC2.lvl