Nethercore mode

Now that the nether is survivable, it would be fun to add a "nethercore" worldtype. Instead of spawning in the overworld, you spawn in the nether, a new challenge even for veteran players. Your main goal from the start is to acquire gold to trade for obsidian so you can make a nether portal. Maybe make it a hidden mode like the "debug" world setting if mojang thinks it wouldn't fit the normal game as well.