I have a mandatory embedded field which have the optional fields in it but i'm able to save the component without any values in it. The requirement is that inside an embedded field, either of the fields should be given. If one field value is given, then other can be skipped but at least one field value is mandatory. For example, In the screenshot below, an image can be specified either by an image URL or by a multimedia image uploaded into CMS. There is no point in forcing the editor to give both but at least one should be given from both. Just by making the embedded field mandatory is not solving the issue.
Note: I can achieve this by adding some logic through event system but i have such embedded field in almost every schema in my system and handling it through even system will highly affects the performance of CMS. Any suggestions or work arounds except event system would be of great help and much appreciated. Thanks!