Though the USAF is desperately short of tankers - and especially KC-135Rs, there are apparently three sitting in the boneyard that we can have. These are the aircraft that will be converted (taking an unknown period at Tinker AFB, followed by 18 months at E-Systems, each) for the RAF.
I'll bet they're in great condition.
And they'll cost more than the Nimrod R5, and cost more to operate.
Apart from that, good plan, crack on!