I read that already, do you know how much that amount of platinum, iron, silver etc would weigh? Tony would be physically unable to move and the constant effort of the Extremis to stop his body from being poisoned would keep it busy 24/7.
Nanomachine handwaving doesn't really cut it.
Bleeding Edge is what RoJoHen imagines
Frankly, Bleeding Edge sounds like it was written by someone who failed biology and wanted revenge.