well that is an interesting concept and proposition.
Organic juicing with a wide variety of vegetables/fruits at the 20+ day stage of a water fast, should replenish most if not all electrolytes/vitamins/minerals/amino acids (proteins).
My own opinion is that it will continue with the detox but to a lesser degree; continue with the healing/repair but to a lesser degree; continue with weight loss; and replace many of the nutrient reserves as well.
Water fasting can then begin again, but only after a substantial amount of time for the juicing to accomplish its goals (say 7 to 10 days)
It does sound to be a good idea (in my opinion) to prevent electrolyte deficiency or other deficiencies that may arise on a prolonged fast.
"How long can the body go without solid protein?"
In the words of Harvey Diamond.....in Fit For Life........
"Do you know of anyone who has a protein deficiency?"