The problem with that argument is that the purpose of the CAS use case isn't to wage an air campaign - it is to wage a ground campaign. That mean the plane will

The problem with that argument is that the purpose of the CAS use case isn't to wage an air campaign - it is to wage a ground campaign. That mean the plane will have to be able to stick around in the air for more than a trivial amount of time. Which in turn means that there can be hidden or mobile air defences that may get deployed while the fight is ongoing.