Do you think this would have been a better ending?

Interesting. It would have given Nick the ultimate moral dilemma of having to choose between Catherine, the lover he was obsessed with and Gus, his best friend. Maybe he would end up in some situation where he would have to decide between one or the other and Catherine would threaten Gus' life and say something like, "It's me you love Nick, not him!" Then Beth would confront Catherine, by stepping out of the shadows, and force Catherine to admit that she misrepresented their affair to Nick (the one they had in college) and that Catherine was the one who had been obsessed with Beth, not the other way around. Then Nick would see how manipulative Catherine was and feel forced to kill her. Beth would be waiting with open arms to "comfort" him.

Or how about the lesbian lovers twist? Beth and Catherine were still lovers all along; Beth was as deranged as Catherine, but unlike her or any of Catherine's other lovers (like Roxy or Hazel) had never experienced the "ultimate" thrill of killing a person. Catherine tells her there's nothing like it, so Beth becomes intrigued and they look for a target. Johnny Boz was just the tip of the iceberg; the ladies would need the ultimate "dupe" to manipulate and eventually kill. Beth finds the target in Nick; emotionally and mentally unstable/vulnerable and prone to many vices (sex, has already killed people, drugs, etc.). She seduces him and then deliberately drives him away with her "clingy" behaviour (which is all a ploy). Catherine then enters the scene, killing Johnny Boz to attract the police's attention and toys with Nick's emotions, making him fall for her and the two ladies reveal their true intentions at the very end and it is only then, when Catherine and Nick are having sex, that Beth enters the room and Catherine offers him up to Beth and encourages her to kill him with an ice pick, like Johnny Boz was. In his final moments, as Beth is killing him, Nick realises the terrible truth. The ladies have it all worked out. They'll pretend that Catherine had been involved with Nick for a long time and make it look like he killed Johnny Boz in a jealous rage and then Gus can take the rap for Nick's murder. Then Catherine and Beth will disappear to the South of France, under assumed identities, to live a life of luxury.

Maybe I've spent too much time thinking about this?? 😀

Don't let anyone ever make you feel like you don't deserve what you want.