The moons appear useful as dungeons. Make them dungeons with ore-specific nodes and mobs. eg: Selentine Moon would have iron and Stone Nodes that drop a % of Selentine, PvP would be global with no protection zones, mobs would be at the level of the ores' use in crafting. This will open space for noobs and tower defenders on the main map, while giving hardcore PvP space as well.