Cheat mode
Simply start or resume a campaign from the main menu. Now return to the main menu and select the single mission option. Then choose any mission, go into the briefing, and click on the armament option. Select a Herc, go back to the briefing, and cancel the single mission. Resume the campaign from the main menu, now play the first assigned mission, then save the game. Then load the saved game to access every Herc and it is fully armed.