I managed to change the loadouts of air force fighters in F/A-18 through hex editing. The following AA loadouts for USAF fighters are now:
F-15C
Full Anti-air
4 x AIM-120 AMRAAM
4 x AIM-9X
Late DS Eagle
4 x AIM-120 AMRAAM
4 x AIM-9M
Early DS Eagle
4 x AIM-7M
4 x AIM-9L
and the F-16C
Full Anti-air
4 x AIM-120 AMRAAM
2 x AIM-9M
I discovered that the values for the AMRAAM, AIM-9 and Sparrow were 26, 25 and 23 respectively. The value quantity was 0 and then the number. It seems that you can change either the type of weapon, or the quantity but not both. Therefore, for the F-16C, its not possible to have a full anti-air loadout of 2 AIM-120s and 4 Sidewinders, because then the type of MRAAM was changed as well as the quantity (from Sparrow to AMRAAM and then from 4 to 2 missiles). I tested them out extensively so far and they seem to work out fine.
Anyways, just thought you guys might like to know.