Multi-language support for custom HTML emails

The current feature to send notifications in customer's language works fine, it's very easy to set-up.

However, if I want to keep the same email's style of my store it's mandatory to upload a custom HTML template. The issue is the template will be the same for any languages, I mean, all notification will be sent in only one language.

It would be great if the text within e.g. "Email alert subject" or "Email alert description" is a liquid variable like {{email.alert.subject}} or {{email.alert.description}} to implement these variables within the custom template, so Restock can send the notification full customized and selecting the properly language as the app does currently.

Thanks