Not really. I don't know of any good way for FFF to do that.
The FFF anthology feature can be used with story URLs from different sites, but that doesn't 'fuse' them.
Something I use myself for a handful of stories that appear on both SpaceBattles and SufficientVelocity is keep both stories in my library, but not include the main story in one.
Example:
Code:
[https://forums.sufficientvelocity.com/threads/a-darker-path-worm-fanfic.107715/]
add_to_skip_threadmarks_categories:,Threadmarks,Informational
add_to_replace_metadata:
title=>^(.*)$=>\1 SV Omakes
Depending on the story, there will still be duplication of cross posted omake/apocrypha, but at least the main story isn't duplicated.
Theoretically, you could use that with anthology, but I haven't tried it.