For the tags: it would be really good to differentiate the tag itself from its url, so that while the tag name should be multi-language, as it is now, it should be possible to keep the url to strict a-z letters if choosing so.
Example:
“disposition à payer” (French with special character in the middle). This currently produces a URL as disposition-à-payer also with the special French character. But it should be possible that the tag name is disposition-à-payer but that the url is instead disposition-a-payer. At least I should have the choice of choosing.
Special characters in URLs is not good SEO practice (yet) and in quite a few countries it is not the norm. People expect the a-z URLs, not the special characters.