instead of creating completly new islands its already possible to create a new map only using huge ones. "island mover" makes u able to create a map, using the already existing huge islands, but missing out the small ones. maybe this is gonna be a comromise. the tool is easy to handle and the interface is english as well. just run the application, compile the map by your own wishes, and put the saved files in anno1404 directory. start a new endless game, set the size of the map as soon as the size of the islands on huge, and u will be able to play a map just containing huge islands
link:
[Tool] Karteneditor (Island Mover) aktuell: v0.9.2 
