In the Ukrainian Wikipedia, all templates of the {{user-xx}} family have their own design (https://uk.wikipedia.org/wiki/Вікіпедія:Вавилон). To simplify the transition to babel I think we can let communities choose the style for the templates, but for this we need to be able to define the template through CSS.

I think it's worth adding a unique class for each language version of the template, for example: .mw-babel-box-ru. Taken together with the level class, this will give the exact definition of the template you want.