I’m not that against the idea. I just don’t think it’s marketable to put the main hero in a relationship with the villain that killed Han Solo and was the primary antagonist of the previous 2 films. It’s not impossible, but there has to be a good reason to go in that direction, and it would piss off a lot of people.
Luke still forgave his father for the past twenty years of disaster and chaos he committed. Even Padmé forgave her husband for what he had done before she died. I believe that Ben regrets killing his father. The audience is supposed to view him in the same way Rey does. Feel more sympathy with him and hope that he will return from the Dark Side.