I fail to grasp that your request is considered about the current handling of environment variable. /etc/environment is a list of environment variable. It used by pam_env. Then, which init scripts do you suggest? Can that script handles LANG setting easily rathar than the current scheme?
Maybe you could create a new init script /etc/init.d/locale, just as Red Hat does. It has the advantage that the lang has been set up with booting already then.