Lol. xdAll true, no doubt.
For Katon, I don't think Fire Release would harm Gedo Mazo. But if it can, Tobi can Shinra Tensei it away.
For Amaterasu, Tobi can touch it and turn it intangible, or maybe blow it away with Shinra Tensei.
Shinra Tensei vs Roar: Damn, wood would be everywhere. LOL
As of now, I really don't see a way Madara can dispatch Gedo . . Unless he Amaterasu'd in the face, but it can clared off via Shinra . . Idk at this point. Not sure it has any weaknesses. :shrugs:
Edit: CT maybe.
Possibly. Unless Gedo breaks free. It would have the 7 Bijuuu within it so . ..it can tear apart the forest. it wont completely destroy it. madara could just remake the forest. madara can make mokuton come up from underneath gedo mazo and restrain it. madara can also work with mokuton clones to achieve this.