Someone with more background than I should weigh in regarding the specs of the KC-10, KC-135 and KC-X, but I suspect that in the design universe of payload-speed-range, the KC-X is asking for more than either of the previous designs could deliver. I'm good with that concept. The USAF should have the best idea of what kind of tanker they need in the 21st century.
The bigger problem is twofold. First, USAF has totally screwed the pooch in its attempts to award a contract. I've seen it done badly any number of times, but I've never seen it done this badly and this consistently for a given procurement. Second, this ENTIRE procurement is about politics and lying to the American people. The morning drive in the DC area is an amazing experience. In addition to the madness on the highways, we get radio ads for government procurement. Computer services, ships, and aircraft are hawked like they were just the most normal thing to be spending your money on, don't you know. Lately, the Boeing ads have been incredible half-truths and apples v. bananas comparisons between their design and the EADS plane. Whether the subject is the percentage of American content, whether Americans or foreigners will be building the plane, or any other topic - the fact that Boeing is now a Chicago-based company is pretty obvious. About the only thing they haven't done is to publicly threaten to kneecap someone. As an example (and I don't have the current figures), most Americans are probably not aware that in the original proposals the EADS plane would have had more American content and American labor hours than the Boeing plane, and OBTW, it carried more fuel to dispense to its fighter-customers.
Ditto! Remember this goes back well over 10 years. The USAF almost had Boeing continuing the 767 line for this and other platforms (including a Joint STARS/AWACS variant), but the entire effort started over after the scandal with that female General. She went to jail if I am not mistaken. I was OK with the competition for the KC-X until Northrop Grumman dropped out. Now it has to be Boeing, IMHO.
It did so by exceeding clear size requirements of the original RFP...that's a no-no.
USAF had requested a specific replacement for the 135 and not for the KC-10. The original selection had to go outside terms of the RFP, which should have triggered a new proposal cycle from both parties.
Now, a decade later, a split procurement might make sense but a 50-50 split would probably be too heavy on the larger AC. And, remember that any reduction from the tendered numbers will increase the unit cost for each version.