1. Killing the Enderdragon's possible in Vanilla Minecraft, you know.

2. Have you heard of improv?
Anyway, I'm thinking of starting in a Minecraft village, where you either can go exploring, hunting for Enderman, mining Obsidian to build a portal to the Nether so that you can get a crucial ingredient to make Eyes Of Ender, which is required to open a portal to The End, or you can go buy stuff from the villagers using the local Minecraft currency of Emeralds (Although the starting money would be in Karjamian Dollars, the Karjamians have exchanges for a vast variety of currencies like the Emeralds. How they'd get hold of other currencies in order to do exchanges depends on the currency (in this case, they're actually mining them in Minecraft worlds) ).
I'm also thinking of having a race of beings encounter able called "Minecraft Players", which are beings in the shape of "Steve?", the protagonist and player character of Minecraft.
Said beings encounterable include "Sky The Kid" and his friends "Deadlox" "Husky Mudkipper", "Jerome", "Ant Venom", "Gold Solace", "Bajan Canadian" and "Ultimate Minecraft Universe" as well as beings like "Bodil40", etc.
Others may be included as well, and in fact, I might allow Minecraft Players to be a starting race.