[quote=Crimmy]
What defines a Gundam exactly? What if it's a Gundam that is mass-produced, and is pretty much a grunt?
[/quote]
Well, the most famous one among them is called [b]G[/b]undam, [b]M[/b]ass Production, so... :p

I think OP meant or implied that we can only use mass-produced MS, so no Gundams as we know it (from RX-78-2 to all those insane stuff from G Gundam), on GM, Zaku and maybe some of the more advanced ones.