Rough technical way of implementing that:
- the saveAction and publishAction event facades are already "enhanced" in Content Edit View to receive the fields values and the UI validation state of the form. There, it could also receive a callback that is supposed to be called when the server detects some validation issues.
- this callback would given back the errors in a structure way to the Content Edit Form View which should then give those to the concerned field edit views.
One thing to take into account at some point (not necessarily in this story): we are also saving the draft before a preview