LexManos Posted October 17, 2015
There is a mod out there called Cubic chunks, which tries to add more height to the world. However, this is not supported by forge and causes major issues with mods and saves because its a fundamental change to the world format/game format. This is not 'simple' and not something that we'd support.
I can't see an easy way to implement this in one dimension either; you'd have to make your own versions of every single class for everything from chunk loading/saving to rendering, and any classes that use them, a lot of which have hard-coded limits (e.g. a check for y >= 0 && y < 256 when accessing a chunk).
Also, simply filling in all blocks is not a good test since there is nothing to render; the game only renders block faces if they are exposed and/or transparent blocks (try filling in the area with a block like fences). Likewise, a world with caves or a lot of trees (think jungles and the lag issues many people have in them) will run much slower than one without them (even with occlusion culling the game still renders the geometry in a chunk, it just doesn't send it to the GPU unless it is visible, and it doesn't work that well in forests, or underwater kelp forests since there are many gaps and/or transparent blocks that let you see the chunks behind them so they can't be culled).