The upcoming editing form for entities will allow to edit translatable and non-translatable values on the same form.
To maintain the usability the form elements should have a way to indicate whether the are language specific or not.
Introduction of a new form element property e.g.
#multilingual that allowes to define whether a field element is language specific or not.
The behavoir should be equal to the
#tree property, which means child elements inherent the property value from the parent but can override it if necessary.
User interface changes
postponed on this issue.