Hi Nicolas,
Thank you for contacting Syncfusion support.
In Essential JS 2 we have already logged a feature report “Load locale object from files for Localization Improvement” regarding this localization support and it will be implemented in our upcoming main release volume 3, 2018 which is expected to be out, in the end of September 2018.
Please let us know if you require further assistance on this.
Regards,
John R