I think it would put Rey on an even footing with kylo on an emotion level, in the hanger scene you can have Kylo tell Rey “we are heirs of the darkside and we will take it’s throne” really lean in on the similarities between them -the “dyad”. this would make the ending far more impactfull (especially if we make ben live) as we have them both reject their innate darkness and begin the future with the light-It rhymes.
And then Rey still struggles with the dark side as if the fact that she rejected her inner darkness meant nothing at all, just like Luke in The Last Jedi where he has a dark side temptation to murder the sleeping Ben Solo as if rejecting his inner darkness after realizing that he is following in Vader’s footsteps meant nothing at all.