Interesting stuff. Remember the USAF are not fielding the F-35 as their only system but rather as part of a system...F-22/F-35 and for years to come F-16/F-15 types. The USN will field F/A-18E/F and F-35C. UCAV to come to both services.
Countries like Australia are stuck with small numbers of aircraft and cannot afford a Hi-Lo mix..