I was planning to try the 5/3/1 program, too. Do it twice a week, no assistance work, but adding in my olympic lifting class which lasts only 6 more weeks. I don't have any answers to your questions, but I like your thinking. I think you put into words why I thought it might work better for me: the slower pace allowing for doing cardio and my olympic lifting class without screwing up the program, perhaps the ability to get some weight loss at the same time.
Female, 5'3", 48, Starting weight: 163lbs. Current weight: 135.
Starting squat: 45lbs. Current squat: 145 x 4.