From the department of long shots:
Hmmm, you could perhaps skip the s:validate tags and use programmatic validation?
Or perhaps have a skipValidate boolean in your entity that you toggle and then use custom validators to trigger only when they are true?
So, you want to skip the validations when you write to the model? Or when you persist the model to the database? If the former, then you can't use s:validate tags (I worked around this once by calling the validation manually on clicking the next button) - you need to be careful to attach the correct error message to the correct field though...