Fukua's story is actually a "boss rush" with all the characters in the game (as of the original 2E release) in the reverse order of when they were made. That's why Boss Marie is in the middle just before the original 8 characters. If we get playable Marie I think they should just add her at the beginning of the story as the latest character along with all the new DLC characters to maintain the theme.
Changing it would be strange, story-wise. Same for Umbrella.
But Eliza, Beowulf and Robo-Fortune never appeared in the stinger in her story mode