Copper Miner Action $0
+1 Action
+$1
_________
In games using this, remove all Coppers from the Supply. Replace each player's starting Copper with Copper Miner. Counting the starting Copper Miners, there are 120 Copper Miners in the Supply. All cards that refer to Copper are considered to also refer to Copper Miner.
Silver miner Action $3
+1 Action
+$2
__________
In games using this, remove all Silvers from the Supply. There are 80 Silver Miners in the Supply. All cards that refer to Silver are considered to also refer to Silver Miner.
Gold Miner Action $6
+1 Action
+$3
___________
In games using this, remove all Golds from the Supply. There are 60 Gold Miners in the Supply. All cards that refer to Gold are considered to also refer to Gold.
Platinum Miner Action $9
+1 Action
+$5
___________
In games using this, remove all Platina from the supply. There are 15 Platina in the Supply. All cards that refer to Platinum are considered to also refer to Gold.
Other card possibilities: Banker, Eunuch (in charge of Harems), Hoarder, Lord Privy Seal (in charge of the Royal Seal), Fence (sells Contraband), Donald X (has a 'Stache), Counterfeiter, Shaman (provides Talismans), Artist (creates Masterpieces), Lendor, 49er (finds Fool's Gold), Witch Doctor (sells Amulets), Treasurer (produces Coin of the Realm), etc.
Dominion would probably be worse without Treasure, but how much worse?