Automatically rearrange pages in document

We have some documents that come into our Grooper process where we would like to have the pages rearranged automatically. The main content is one of our known multi-page forms. Say Form A and Form B. The forms may come in with a number of cover letter pages and some supporting pages. We would like these moved to the back of the document, so the form is front and center. Sometimes either the cover letter pages, supporting pages or both are not in the document.

The cover letter and supporting document pages are 'unknown' page types. I don't think it would be feasible to have Grooper try to recognize Cover Letter and Supporting Page types. We should treat them as 'unknown'. Basically move all unknown pages to the end of the document.

The pages could look like this:

1. Cover Letter Page 1
2. Cover Letter Page 2
3. Form Type A Page 1
4. Form Type A Page 2
5. Form Type A Page 3
6. Supporting Page 1
7. Supporting Page 2
8. Supporting Page 3
9. Supporting Page 4

We would like the resulting PDF that is output from Grooper to have the pages re-arranged as follows:

1. Form Type A Page 1
2. Form Type A Page 2
3. Form Type A Page 3
4. Cover Letter Page 1
5. Cover Letter Page 2
6. Supporting Page 1
   
7. Supporting Page 2
8. Supporting Page 3
9. Supporting Page 4

What is the way to best accomplish this?

As a bonus: The forms have instruction pages. Sometimes these are also submitted with the forms. If we get those we would like to discard them. I currently do this by recognizing them as a page type and then in the export step only exporting form types in one sub-tree of the data model that has the forms we care about.