I think the idea has promise, but would be very tricky to implement.
I’d keep part of Obi-wan’s ghost scene, so that it’s established that Luke has a twin sister. He simply doesn’t think that Leia fits the bill.
Here’s a potential ending:
-DS explosion. Han and Leia don’t speak.
-Ewok celebration. Luke returns, sees the ghosts. Perhaps there’s some ghostly echo from Ben to remind him of his twin sister.
-Luke and Leia discuss his family.
‘Luke what’s troubling you?’
‘Vader’s here. I’ve felt his presence. He’s my father.’
‘Your father?’
‘The Force is strong in my family. I have it. My father has it. My sister has it.’
‘That’s why I have to go.’
‘I wish I could go with you.’
‘You’ve always been strong.’
-Luke leaves, Han arrives and hugs Leia.
-Luke burns Vader’s suit.
-Pan up to the stars, and End Credits
Unfortunately, I don’t know if there’s a way for TFA to work without the knowledge that Leia is his sister, since Kylo’s entire being is built upon the assumption that Vader is his grandfather.
The easiest way to sever Leia’s blood relation to Luke is by recognizing that Ben could have easily been misleading Luke to keep the true ‘other’ safe. No fanediting is needed, except in the case of Episode 3.