Currently the culture method will search directly for a "fr-FR" property in the kendo.cultures object. If you load only "kendo.culture.fr.js" script, then you will need to set the culture like this:
I will log your request for further consideration and investigation. If other users need such functionality we will schedule it for implementation.
All the best,
the Telerik team
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI