Very accurate post, Engines.
By the way, I was rooting around in the 'tubez the other day and found this:
http://www.dtic.mil/get-tr-doc/pdf?AD=ADA292094
It also locates key decisions (including the single engine) within the OSD. However, one antecedent that is easy to overlook receives little attention in this document: the export angle.
Back in 1987, I recall, Weinberger memoed the Navy and AF to the effect that their new stealth aircraft (ATF, NATF, ATA) would all be too costly and too classified to replace the Viper and Hornet on the export market. That kicked off a series of studies that led to the Japanese F-2 and the Super Hornet... But neither was really expected to be the full replacement. That became part of the JAST plan.