regulate the amount of GPL in the economy
Something like diamonds then. Ten percent of the best mined diamond are allowed to enter the market and ninety percent are ground up for abrasives, used in electronics, optics, or stuck in a warehouse.
Replicator latinum (if possible) might not have a detrimental effect on the value of "natural" latinum if the two could be told apart. It would be like the effect of synthetic diamonds on the diamond market, which is basically none. People want natural diamonds.
Someone walks into Quark's bar with replicator latinum, and the scanner in the door frame screams bloody murder.