I would like to embed metadata field values in text layers using metacommands such as those used in Lightroom's Filename Template Editor, for example, {Title} or {Creator}, etc.
Early versions of Photoshop did not have direct manipulation of text. You typed text into a dialog box and it was added to the document. A script could do that and make substitutions, or could be run on a layer once entered. I do something similar in my PDFExport script for Bridge.