I believe that a nether roof biome (or dead zone biome) should be added to minecraft, believe this mostly because the people at mojang keep patching out ways to break bedrock and the community keeps finding more. This biome would be the first biome to have a vertical biome separator( if you know what I mean) and it would also be fully covered with a sort of black desert that resembles ashes, the blocks naking up this biome would be unspawnable to reflect the bedrock that was previously there. And there would actually be a sky with a giant sun (just to add another reason as to why the nether is so hot, and would also explain why evrerhing is ashes; it just burned up). This would also explain the lack of mobs, just a tad too hot for them. There is also another feature that I also think would be cool at first but annoying later on, when in this biome you get the nausea effect( because of the heat) but only a dilluted version that for the first five minutes of being up there you wouldn't even notice it. Also up to a certain time of being up there you start taking damage. I like these 2 last ideas but feel like after the 3rd time you start getting the nausea effect while building your gold farm it'll start getting annoying.