I think an excellent edit would be to cut out the back stories of Finn and Poe, at least initially. Maybe open the movie with Rey and her life on Jakku and then she runs into BB8 and then eventually Fin. This would add some mystery as to the characters and what is going on. We do not need to know that Fin is a stormtrooper and instead we discover that. This would not be a bad thing. Try and keep the focus completely on Rey and make Poe and Finn solid supporting roles.
That’s a great idea! Perhaps footage of Finn’s betrayal could be played as a flashback while he’s in a coma in TLJ?