We can produce materials for free, materials that make up the munitions, and we can produce the munitions for free - and you want munitions & materials rewarded for free? You say "so the reward is the result of game play" - we're already getting materials from matches.
Kinda makes the manufactory lose some of it's strategic purpose.
ps: If this happened - which I'd certainly welcome - I can see the same arguments people made about NTGs:
"I've been searching for an hr trying to find thermoplastic and all I get is processors"
"I've received 10 superconductors in the last hour and I can't even use them yet"
"Can we have a building that allows us to sell munitions"