"You couldn't even begin to localize templates like this without rewriting them"

How come? If your base HTML templates are say python or ruby templates they could be localized fine. And if the JSON content your parsing with Walrus comes from the same backend and is also localized where's the issue?

It's mustache with some view logic sugar which makes a lot of sense as far as i'm concerned and would allow your HTML templates to be mostly 'logic free'.