While Ubuntu runs fine on low spec hardware, the minimal system requirements are still pretty high. Ubuntu will not run on truly embedded hardware, the smallest Ubuntu root filesystem in the form of ubuntu-core still uses more than 100MB diskspace when unpacked. A tool to create even smaller footprint filesystems already exists in the form of initramfs-tools which has hooks and scripts to allow the addition of any binary from the underlying Ubuntu filesystem (or chroot) it gets executed from.
Scope of this spec is to research, plan and implement the creation of a truly embedded rootfs builder which creates an absolute minimal filesystem that can also run on hardware with extremely limited diskspace by using parts of the existing infrastructure from initramfs-tools (i.e. copy_exec and friends).