You're mostly correct on relievieng the digestlive system but you can not ignore the issue of live enzymes that aid the system in cleansing and the nutrition part that live juices provides vits and minerals to help us function while we fast and aid the system rebuild.
Have you considered the Master Cleanse? You already have a citrus juicer and that makes it really efficient where you can make your whole daily ration for the day in the morning n less than 30 mins. I really think from all views that you would be much better off and accomplish your cleansing goals much more efficiently with the MC than doing dead bottled juices.
Have you tried any of the oxygen based colon cleansers like OxyPowder?