I would disagree that sex with Anna would be the end of the game, except for really die-hard Anna fans. As with Lucy, it's a case where I'd be okay with not having sex with her for a while, had things not progressed to where they have. Anna lost her job. She was raped or at least there was an attempted rape, depending on the player's choices. She's dependent on her son to pay the rent and other expenses, and she's letting him sleep in her bed. Mentally, she's somewhat broken now, and honestly Bobby should be able to do whatever he wants with her with only minor resistance if we're going the rape route. If we're going corruption, Bobby just has to push her over how he has to support her, and it seems like she'd reluctantly cave to increasingly sexual stuff with him. For Bobby to corrupt her any more seems pointless. His putting her in submission poses as she slept in one of the last updates just seemed silly. Again, it's a case where Rainces pushed things farther ahead then they probably should have, and then just stopped meaningful forward progress on it.
Bobby's complete inability to either actually corrupt anyone or rape a passed out or tied up woman is just frustrating, and for this to continue makes even less sense than the scenario you suggested. For Bobby to not rape Lucy when he knows multiple ways of incapacitating her doesn't really play into the "bad" part of him, nor does his inability to push things with Anna. Have him get Lucy drunk again, and then have his way with her. Have him shame his mother into having sex with him. Have him blackmail Liza into sex with him. Have him grab Lucy and carry her back to his room and fuck her senseless when she tells him she would never sleep with him.
Bobby's not bad. He's pathetic. Make him the actual bad boy the game promised, and not the loser he looks like.