A lot of people mention how the height limit is ~256 blocks and the terrain hardly goes 150 sometimes. So why not make it possible to build on clouds? I mean we can already build on air, imagine a house that just floated around; or once you build on a cloud it will stop moving.
The only problem with that would be when you build on a cloud that it would stop, as you said. Then clouds would get stuck in people's homes. It seems like it should be an SP mod and not a vanilla addition.
Making a house made of clouds would be so cool! Maybe other clouds would float through your house and your house moved, and they could invent codes to do the opposite. I do not think it should be in the original version, though, so it should be a mod. Oh my gosh! SKY REALM MOD!!!!!!!!!!!