Well thats not true. if you set the type of missions in any campaign data.ini for that aircraft to 100 and anything else to zero. I'll bet you get your intercept missions.
Like this
//----- Player Unit
[AirUnit001]
AircraftType=F-105D
Squadron=7TFS
ForceID=1
Nation=USAF
DefaultTexture=USAFSilver1
BaseArea=Spangdahlem Airbase
BaseMoveChance=0
RandomChance=100
MaxAircraft=16
StartAircraft=16
MaxPilots=16
StartPilots=16
Experience=100
Morale=100
Supply=50
MissionChance[sWEEP]=25
MissionChance[CAP]=25
MissionChance[iNTERCEPT]=25 <----------- change this line to 100 and all others to zero
MissionChance[ESCORT]=25
MissionChance=80
MissionChance[CAS]=25
MissionChance[sEAD]=25
MissionChance[ARMED_RECON]=25
MissionChance[ANTI_SHIP]=0
MissionChance[RECON]=0
UpgradeType=NEVER
Supply[001].WeaponType=M117
Supply[001].Quantity=2880
Supply[002].WeaponType=Mk82
Supply[002].Quantity=1440
Supply[003].WeaponType=Mk84
Supply[003].Quantity=240
Supply[004].WeaponType=LAU-3A
Supply[004].Quantity=480
Supply[005].WeaponType=AIM-9B
Supply[005].Quantity=240
Supply[006].WeaponType=CBU-24B
Supply[006].Quantity=480
Supply[007].WeaponType=Tank450_F105
Supply[007].Quantity=480
Supply[008].WeaponType=Tank650_F105
Supply[008].Quantity=240