aw33com,
What you are telling us is very interesting, are you a Mirage pilot ? Or a Mirage mechanic ? Or a Mirage designer at Dassault ?
It's very interesting because when we take a look at the real aircraft manual ("It takes 5 minutes to Google it") we can see that the PCA MAG button is used to start the magic MAV mode and not to select them.
Same with the PCA CAS button, it is written that it selects the guns in Air to Ground mode (CAS = Canon Air-Sol = Air to Ground Gun).
Also in this manual, we can read that the AA gun select and magic select are situated on the throttle on a 3 position switch with PCA select as the center position.
Also, Razbam is currently working with the AdA (Armée de l'air = French Air Force), that is currently the only Mirage 2000C user, to correct and improve the module. And they have helped with the changes of this update.
So if you have some informations that can contradict all of the above, please, share it with us :).