?
This sounds like a good candidate for a Reporting Action, but with the ZippedHtml option. Although the report outputs a binary file, you could write an html file to disk with a hyperlink to the file, and use that as the index. Both would be included in the zip file, and present in the report. If the FPR file is large, it might be better to save these on disk so it's not saved in the database.
There are some additional built-in reporting actions that are not on GitHub; you can find those thru Reflector or something or fill out the Source Code Request Form.
There are no background actions of course, but one option could be...
Trigger that watches Promotion Completed event
Runs report in background; adds report to the Build using the BuildOutputs_AddOutput action
Add a Promotion Requirement to verify report has completed
hope that helps. I'd be curious to see what you come up with.