I think this would require a great deal of equipment to have on hand in advance. Other problems would be increasing incidence of latex allergies, difficulty in long-term storage of latex tubing (have you ever seen old latex products, especially if exposed to high environmental heat). The incidence of IV related complications, even with sterile single use products can be high (phlebitis, catheter related infections, etc).

There is experiential evidence that oral rehydration is superior to IV rehydration, especially in suboptimal environmental conditions (Google: Dilip Mahalanabis ,director of International Centre for Diarrhoeal Disease Research, Bangladesh and his experience with rehydration in refugee camps during the Bangladesh Liberation War and Indo-Pakistani War of 1971.
Another alternative, if unable to take oral fluids, might be: Hypodermoclysis. This is an older form of non-oral hydration little used in human medicine, but sometimes inveterinary medicine. It is technically easier to institute as venous cannulation isn’t required.
Unfortunately in survival situations if someone is ill enough or has injuries such that oral rehydration isn’t possible, they may not survive.
Just my thoughts, with 35 years of IV therapy experience, seen all the bad things that can happen even in well controlled situations.