So I looked at the cancelled game Fallout 3 Van Buren, I also looked specifically into their creatures and noticed many such as 'gehenna', and most of the creatures from Van Buren. these creatures which arn't used due to the game being cancelled could be reused and implemented into Fallout 4 through DLC or content patch, though keeping to the lore would be sensible. also floaters, i miss them.

I have no idea about the legal stuff behind this or what it would require so if you would like to fill me in that would be nice.

Thank you.

Bethesda owns the IP, they do as they wish with it