Modifying document without uploading to the database

Is there a way to update a document without uploading it to the database?
The ultimate goal is to perform validation before uploading to the database (see #1984 and #1287).

I would like to do something like this:

document.modify(upload_to_db=False, **update) # or .upload()
document.validate()
document.save()

# or 

document.modify(upload_to_db=False, **update) # or .upload()
document.save(validate=True)

How to get the updated document without upload?
Recreating the new document is very painful while supporting the "Django-style update keyword arguments".

The only solution I have so far is to call modify() to get the new document, validate the document, re-upload the old document if the validation fails.

Start by tracing the existing Document.modify and Document.save behavior, then read the related issues #1984 and #1287 for prior discussion. Done should provide a supported way to apply Django-style update keyword arguments, validate the resulting document before database upload, and preserve the existing save behavior.