How to Implement Multi Language Email?

Summary:

The requirement is to send out multi-lingual email content based on the country/language (header attribute) selection on quote.

Currently we are maintaining all the translations in one single template (As we have more than 60 languages) and trying to send out email on step transition (using Define notifications and associating the Email template there), but there's no flexibility to identify the language in which the email translation should be sent out, as a result no matter what country/language is selected on the quote, Emails are sending out in Default (English) language.

Please note: the email content includes hyperlinking of URL on some texts and also expects "Proposal" to be added in the email as attachment.