I generally like the idea. Not that I have much use for it at the moment, but maybe others will?
However, I wonder if settings like the filesystem etc. should better be done via function-calls as they might allow optional checking for validity. E.g. the filesystem might *optionally* be checked against a list found in a file, by standard maybe /proc/filesystems. Also blockdevs might optionally be checked if they exist etc. Optional because maybe you edit the fstab for a machine different than yours which might support different filesystems or so.