Access Database in Core class

Like @jrklund said a hook could solve this issue.

But I am wondering why you are using JSON and htacces for this? Is there a specific reason for it? If not you could easyly use the pre build language files section of CI. Then you just need to log your user language in the session and set a standard language.

In config.php :: $config['language'] = 'english';

And then add your language files in the system.

example

PHP Code:

$lang["hashtag"] = "#";
$lang["thumb"] = "Thumb"; 


And then to use it is as simple as

PHP Code:

<?php echo $this->lang->line('hashtag'); ?>

I am honestly wondering why you are over complicating things with json and htacces ...