Until the eliminate the dollar bill, the dollar coin is doomed to failure.
The biggest problem with the dollar coin for me is that hardly any vending machines take it. I remember pinball machines used to take the SBA dollar though. I don't know what the government can do to remedy the situation. Maybe just discontinue the bills and introduce $1, $2 (and $5?) coins in large volumes. If the coins are out there in people's pockets, the vending machines will have to start accepting them to be competitive. In Japan, you can walk up to almost any soft drink machine and put in a 1000 yen bill ($10).