I would have cast Jessica Henwick as Rey. She would have no blood relation to Palpatine or the Skywalker clan. Through her hard work and determination and grit, leaning on her skills as a scavenger she would become a Jedi. Proving herself to Luke Skywalker.
And give Finn an actual character arc. He becomes a Jedi leads a rebellion of stormtroopers. He isn’t a janitor, he isn’t the new trilogy Jar Jar or comic relief. He doesn’t exist to just yell Rey!.