If you don't have more gold characters, sure, you can grow or improve your copies, maybe you can improve the skill tree and give keys for one and the copy give the role of team assistant (while you increase your collection or got new characters).
If you have more gold characters, I recommend give time to the other characters that maybe needs experience (to have a good roster to participate on prize fights). Anyway, from my perspective, having another powerful Harlequin doesn't sound bad (but it's just my opinion).