i built a similar deck, i would recommend ancient stirrings to help make sure you get liquimetal coating, also more cheap destroy artifact cards deconstruct is fun because it gives you back 3 mana (although all green)
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4 negates does not seem like enough to protect your piper from removal
Tried to make a standard version of this deck, comments would be greatly appreciated, its right here http://www.mtgvault.com/ViewDeck.aspx?DeckID=193945