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.
There's tons of unbelievable things happening in these movies and tons of things that would kill Stark while using the IM suit , in real life.
The use of Extremis/Bleeding Edge armor will not be a deal breaker... for me that is.