BGen Jack Ledford, director of CIA's U-2 project, James A Cunningham, Ledford's deputy and C. L. (Kelly) Johnson thought it a good idea. (And maybe John F Kennedy and Lyndon Johnson who wanted those and other such missions flown.)
Edit>> Or maybe I don't understand the question.
In-flight refueling feature was used in 1962 and 1963 for several Takhli to Tibet missions by CIA drivers. Distance was too great for the 8.5 hour endurance of the un-refueled U-2C. No doubt, pilot endurance in the old partial pressure suits was pushed toward the limit in the 11+ hour missions. Max endurance of the U-2F (U-2C with IFR) was about 14 hours.