Unless they've radically changed the original, Fantine should hardly be in it.
I was amazed they got Patti LuPone for much a small part.
I have often wondered if anyone has ever been in two shows at once?
Dash on stage in the first act at Theatre A - Tra La La Argggggg! as they get shot!
Then dash around to Theatre B and a quick change for the late romantic character in another show.
They could cut costs in crowd scenes if one show needed a crowd at only the start and another wanted one later in the evening. Rent a crowd!