Yes, well I was wrong really.
If you place the vehicle in the editor and use the slider to remove the ammo it does indeed remove the proxies.
No idea how I forgot about that.
But removeallweapons doesn't work becuase you are trying to remove the weapon when you should be removing the ammo, try removemagazines.
In the init line, put, for example, 'this removemagazines "mavericklauncher"' and the proxies will be gone.........hopefully.
Planck