Você pode querer editar /etc/default/locale
para definir a localidade, pois seu comando de exportação afetará apenas o ambiente atual. Isso não afetará os programas já em execução.
O problema que você mencionou em relação ao grep foi corrigido há alguns anos:
fixed in grep 2.7, released Sep 20, 2010
In multibyte locales, regular expressions including backreferences
no longer exhibit quadratic complexity (i.e., they are orders
of magnitude faster). [bug present since multi-byte character set
support was introduced in 2.5.2]
In UTF-8 locales, regular expressions including "." can be orders
of magnitude faster. For example, "grep ." is now twice as fast
as "grep -v ^$", instead of being immensely slower. It remains
slow in other multibyte locales. [bug present since multi-byte
character set support was introduced in 2.5.2]