Hmmm, try
No, thats not the problem, and I will tell you this, it DID work, the unit will select the AT4Launcher, however, your problem isn't that he won't select it, its that even with a secondary weapon selected, an AI unit WON'T allways switch to the animation untill they are about to fire it. Therefore, the solution would be to add this line after/under your first one (which is fine, leave it):
spetz2 playmove "Weapon"