Personally I think that training a body part only once per week is to little. Especially when it comes to legs, at least with uppper body there is some decent overlap but still not enough. Even if you do from the floor deadlifts on your back day, I still think that legs don't get worked enough with a once a week split. I like to use a four on one off split. But I think that working each bodypart twice a week could work very well, just remember to drop the volume per workout compared to the once per week split. And you can't replace squats with deadlifts or the other way around. Unless you have prior injuries that prevent you from doing one or both of these movements they should be a part of your training. Get your form right and start piling on the weight!