Now that I think about it, if we go back to Brave (the cartoon), isn’t there essentially a tension between two understandings of bravery? Merida (being young and feisty) argues that bravery is the ability to shape one’s own fate, and to make one’s choices. By contrast, more “mature” bravery involves acting with an eye to the costs and consequences of one’s actions for others. It’s a fine line between rocking the boat and capsizing it.
Both Rumple’s and Arthur’s stories hinge on the idea of “fate,” framed as a prophecy. With Rumple’s story, the origin of the whole coward label goes back to the stigma of being a deserter. Which, incidentally, was due to a prophecy (Rumple was told his son would grow up fatherless) — and I think this might parallel Arthur’s story: by trying to escape the prophecy, Rumple makes it come true. By trying to fulfill the prophecy, Arthur makes a hot mess. So there’s already this tensions of fate vs self-determination there, which I guess connects back to Brave.
What a grown up Merida (upon the completion of the cartoon’s character arc) could really offer Rumple by way of “bravery” is the willingness to accept the consequences of one’s decisions, which Rumple hasn’t always been very good at. In other words, she might teach him to stop experiencing himself as a victim — which would go a long way to helping him accept love more broadly.