Alright, fair enough. I wouldn't ask you to try something like that, but I would suggest keeping the latest version on there(at least, the latest 0.3x), and keep a backup or two around.

Now, -currently-, it should work. Its not as "clean" a restore as before, as I can't do "rm -rf /tmp/rootfs/*" & "rm -rf /tmp/optfs/*" where appropriate without breaking things, but that's been disabled in the latest version, and I -have- done a full restore-to-1.2 -> Install rootsh, bootloader-n900 & tar-gnu -> install backupMenu -> Reboot & restore rootfs + optfs and it -did- work fully.
That's with the 0.42/20100925.
It should be safe enough, as its not deleting any files, and therefor shouldn't be able to break your machine, as it just saves -over- the existing ones.