hmm... Minecraft needs more Dungeon Keeper elements... If you don't know what Dungeon Keeper is, slap yourself.
What I mean is instead of tirelessly building one block at a time, you could instead delete an entire wall of rock depending on your currently equipped device (Pick Axe, Shovel, etc), then replace it with say, Cobblestone. Only an idea, and it would save me time. There are many other elements that could be used from Dungeon Keeper, such as Minions as well, and you could minipulate the skins of the minions *not that different from what you do already with your avatar*, and every bed you build or something else could be considered a "Lair".
If you still don't know what im talking about, go find an extremely old copy of Dungeon Keeper 1 or 2. They were one of the best series in the 90's. You could also find software online probebly using a torrent or 2.