You can place a lot of common settings in a common extension:
Smart example (for sites with only different lang):

$ cat settings/siteaccess/en/site.ini.append.php; echo
<?php /* #?ini charset="iso-8859-15"?

[ExtensionSettings]
ActiveAccessExtensions[]=in_common
ActiveAccessExtensions[]=in_lang_en

*/ ?>

$diff -Naur extension/in_lang_en/settings/site.ini.append.php extension/in_lang_de/settings/
--- extension/in_ber_lang_en/settings/site.ini.append.php 2005-09-30 15:32:34.000000000 +0200
+++ extension/in_ber_lang_de/settings/site.ini.append.php 2005-09-30 15:33:13.000000000 +0200
@@ -1,16 +1,16 @@
<?php /* #?ini charset="iso-8859-15"?

[SiteSettings]
-SiteName=[en]
+SiteName=[de]
-SiteURL=http://www.example.it/en
+SiteURL=http://www.example.it/de

[RegionalSettings]
-Locale=eng-US
-ContentObjectLocale=eng-US
+Locale=ger-DE
+ContentObjectLocale=ger-DE
TextTranslation=enabled

[ContentSettings]