Currently the content model of <origDate> is:
While I recognise its main purpose is for recording of the date of a manuscript or manuscript part, it is a member of model.pPart.msdesc and so can be used as phrase-level content in any number of places. The structured recording of a date happens in the @when or related attributes. The text content could conceivably be the text from the original source that indicates what leads one to believe it is that date. While that is perhaps far-fetched and it is more usually the human-readable form of the structured date (e.g. 'c. early 15th Century'), local cataloging guidelines may require the need to encode special formatting of aspects of this. For example, in Bodleian cataloging guidelines the 'c.' is required to be in italics in the output. Moreover, local cataloging guidelines may require the use of non-unicode characters.
For reasons such as these I would recommend that the content model of origDate be changed to be:
(text | model.gLike | model.hiLike)*