Well, i never claimed that the rules are clear...unfortunately they are not.
I think you can, according to the rules, launch missiles without weapon mounts, the number of missiles that can fit under a normal aircraft should be limited by common sense (4 to 8 missiles, i assume).
This way many of the SR combat aircrafts would make sense (at least more than a combat aircraft with either 1 missile or 1 cannon).
In the case of the vehicle weapons, i really believe they mean "reinforced weapon mounts".
That would mean that you can equip your aircraft with a cannon and some missiles.
Mike