Ask HN: How would a new OS be different?

It seems like all of the new operating systems coming out are really just different flavors built on the unix kernel. If a new operating system were to be built from the ground up today, would it be significantly different? I know the linux core is improved all the time as an open source and constantly evolving project, but I just wonder if given the chance to build something with no legacy to maintain, would an operating system have any greatly different architectures or components?