**They forget that they would need to keep a dedicated 'Q tanker' type fleet for the fuel.***
The KC-135 can be used to refuel other aircraft without any changes. We refueled B-52s and fighters in SE Asia with JP-4 fuel. Upon return to the US we would purge the tanks and refill with JP-7 for the SR-71.
WE used to have to hand purge by draining the spare tanks of JP-4 and put in and drain a small amount of JP-7 to wash out any JP-4 left. The tanks were then considered purged.
The "Q" designation came because later a smaller spare tank was added for an inflight purge. This tank was filled with JP-7 and while inflight this fuel was transfered to the empty storage tanks to wash out the remaining JP-4. It was then dumped inflight. It saved us a lot of time and trouble.
You can still refuel other aircraft with the KC-135Q with no changes other than the jet propellant.
Many thanks for the great info.