"If you use your KC30/45s to do more of the routine resupply from CONUS to FOB then you release more of your C17s to do the short or rough strip role. It's simple logic really."
They now use Atlas, DHL, Evergreen, Kalitta, et al, to haul the routine cargo, at far less cost than borrowing tankers for the job.
Will the KC30/45 haul the dense, outsized cargo the C-17 carries?
"Given the RAF's experience of buying used and converting you are simply wide of the mark here. It is expensive and you have to replace your capability earlier. The reason that the KC135s have done 40 odd years is because they were brand new when brought into service. Buying used is a short term saving against a long term cost.
Buying planes with a third of their hours/cycles left is prudent economics. Look at all the 747 cargo haulers carrying the USAF loads today. They are upgrading to 747-4 to save fuel, not for longer life, or because they are new and shiny.
Even Boeing, with their factory discount, didn't use new planes to make their five 747-400 LCF, Dreamhaulers. They bought used 747-400 for the job.
Trying to justify spending $40 Billion based on ancillary uses shows the weakness of the primary argument - the imagined need for brand new airplanes that will get 15% utilization.
GB