There should be a way to create language-specific SEO URL templates, i.e. have a language switch in the administration page just like in most other settings.

Simple translations of category or product data are already possible via the corresponding .translated property, but it would be better to have full control over how the SEO URLs are generated per shop language.

This would also allow adding translatable strings to the templates (such as substituting special characters in product or category names with a language-specific URL-friendly string), which currently isn't possible.