Edit: I SOLVED IT! Just put this into LAWLauncher:
weaponType="16 + 4096";
For some reason, that works. Everything works perfectly now.I was afraid of that.
Funny thing is, THERE IS a way to get it to act normally. Just add this to LAWLauncher:
magazines[]={"RPGLauncher/or any placeholder","LAWLauncher"};
If you do that, it works -- you can select and use LAWLauncher ammo in the selection screen without it disapearing. Perfect, right? Only it causes another problem.
When I played the Resistance campaign, if I complete a mission with LAWLauncher/RPGLauncher ammo in my inventory, the game crashes as the next mission's about to load. If I drop the ammo before the mission completes, it works fine. If I take magazines= out of the config, it also works fine. Adding more than one magazine to magazines= will cause a crash.
I'm guessing this has something to do with Resistance's weapon pool feature, because I don't get the problem in other campaigns or missions. Man, so frustrating.