Comment 7 for bug 1227520

So I think your best bet here is to change those daemons to fallback to in-place file content changes when atomic edits fail because of writable fs.
If /etc/localtime is already a symlink in the rootfs, you should be able to change its target without much trouble too.

Switching those files to be symlinks in the base rootfs is a bad idea which we initially considered. It's bad because we then have no way to get the original value of those, so we'd need something to create the target with a sensible content at boot time, which isn't terribly optimal. Also symlinks have a tendency to confuse some stat checks in various piece of software (probably not a big concern for timezone/localtime though).