Tankers for USAF Part II

Pentagon paper shufflers are about to release the new Request for Proposal (RFP in mil jargon) on a replacement tanker. USAF is currently still flying the KC135's bought in the Eisenhower administration. Good planes and all, but they have been flying for 50 years and its time to buy new ones.
USAF would like to get a bid from Boeing and a competing bid from Airbus. They figure two bidders will get the government a better price than a sole source buy. Plus the Air Force doesn't like Boeing much, and would be happy to give the job to Airbus. They tried just that two years ago but Boeing had good lawyers and got the contract award overturned.
Technically the job is straight forward. Buy 179 jet airliners, take out the seats and install tanks. This is not rocket science.
For some reason, Airbus is balking. They say it will cost them $100 million to do the bidding paperwork and the RFP is slanted toward Boeing. Presumable Airbus figures they won't win this time, and in that case, why go to all the trouble?
One thing is clear, the Air Force thinks its doing a design and development of a brand new aircraft. They have a list of 372 requirements that the design must meet, 93 more optional requirements, and a fancy computer program (Ifara) that will "evaluate" performance on a variety of missions. This attitude is a guaranteed cost enhancer.
An air liner is an airliner. Airbus and Boeing will propose existing airliners. Either plane would work just fine, both of them have been flying paying passengers for years. Both planes performance (speed, take off weight, range, engine power, instrumentation) is well known and well documented. Both aircraft compete successfully in the international air liner market, which means one is about as good as the other.
The Air Force should procure the standard run-of-the-production-line aircraft. They should not ask for modifications of any kind. These planes don't need modifications, they work fine just as they are. Modifications are expensive, and the expense lasts the live of the aircraft. Standard aircraft can use standard spare parts, widely available and in stock to support the civilian fleet. Modified aircraft need special spare parts which are not stocked commercially. Uncle Sam will have to buy, store, and maintain these special spare parts at taxpayer expense.