I think when you ask why rumpel wanted the curse to happen, you have to ponder why would rumpel create a curse that he didn’t enact himself. This might have something to do with one of the major premises of OUAT: “All magic comes with a price”.
Since we’ve learned from rumpel that this is indeed a powerful curse, then it must have powerful repercussions for the person who enacts it. I think Rumpel has his own agenda, and the evil queen enacted the curse, unknowingly “helped” him and put herself at a precarious position when the price of this magic comes back on her.
Then, the question that comes is just what is Rumpel’s agenda? I think he might be using the curse to bring back someone he loves, either Baelfire or Belle. Since episode 19 centers around Rumpel’s relationship with Baelfire there might be some clues there…
When you look up the name “balefire” it can give some more clues: When a target is struck with “balefire” the target’s existence is completely erased by destroying a pattern, erasing events chronologically in reverse. Balefire can even bring people back from the dead, or rather, prevent them from dying in the first place.
We know time was frozen in storybrooke, and then moves forward with Emma’s arrival. But, what if the clock started ticking backwards so that Rumpel can bring back his loved one? In the price of gold episode he said you can’t resurrect people…but can you force time backwards and undo certain unwanted events?