We strongly discourage this type of manipulation to the training plan. Training is something that needs to fit into your schedule, and missing one workout will not affect the overall progress of your training.
If you find yourself routinely having a difficult time getting in a specific workout, say the VO2 Max Interval days, we suggest that you move things around in the weekly plan. The plan is set up on a weekly progression pattern, but is optimized within each week to give you the most rest between high load workouts.
Move things around to fit your life, but be aware that every workout has a purpose.