I fear there won't be any post-epilogue changes in the upcoming 1.09 patch. :/ Maybe there is a slight chance after the most bugs of the upcoming DLC are dealt with. A Christmas present, so to say.
If there was a REDkit 2, or any kind of worldspace-editor, I'd just create a mod, which places the main NPCs back into the game world - with multiple versions for the different outcomes and upload the files to the Nexus. There would be no new dialogue lines though - but at least they'd be there. Not much work honestly.
Of course, to make them do more than just standing around, walk from A to B to C, do whatever there, walk back to A and being interactable, I'd need an - at least - mediocre scripter...but since there is no such thing as a REDkit 2, there is no point in continuing this post. ;D