add config.wip.fs.temproot.remote.type == none, add config.wip.base.includeInputs, add pkgs.uboot-with-mmc-env, rename config.preface to config.wip.preface
ZFS, encryption (keys, keystore, LUKS), bootFS, ephemeral root (tmpfs, ZFS, F2FS, ...), testing in qemu, options & debugging, ... and many small things
make system's $out/config optional, don't use patches by default