Upload File without creating a new generation

I wish to create an Action for the Document ItemType that

1. Prompts the user to select a file,

2. Uploads the file, and

3. Does not create a new generation of the Document Item.

Use Case: 

A Document, for example at Rev C, are reviewed via the out-of-the-box (OOTB) Document Change Object. Prior to the Release step, a PDF file is generated and submitted to the customer. The workflow is then completed, setting the state of the Document as Released. The PDF is sent to the customer for approval. And a new revision, Rev D,  of the Document is started using subsequent DCO.

Not a problem.

The customer returns a wet-ink or digital signed PDF file of the Rev C of the Document. This version of the PDF is to be included in the the latest generation of Rev C, which most probably will have been updated by Rev D and subsequent generations. It is not appropriate to add the signed PDF to Rev D or later iteration. This process is possible using AML, by

1. Determine the ID of the latest generation of Rev C of the document.

2. Using admin, drag and drop the file into the file vault.

3. Get the ID of the file, after it has been uploaded, and

4. Using AML

<Item type='Document File' action='add'>
<source_id>id of the document at the correct generation</source_id>
<related_id>id of the uploaded file </related_id>

Can the above sequence be done using an Action, a Form with a File Item field or some other method?