Hello! I'm really sorry about how long I went without seeing this. If the site has a way of getting notifications for the forums, I've never found it. Still, I can't apologize enough.
Currently the leaderboards are for All Challenges, and All Individual Character Challenges. If I understand correctly, you're suggesting individual leaderboards for each of the game's 622 challenges? My only concern is that that's a lot of leaderboards for a a lot of (extremely short) challenges that should ultimately take about the same time. The number of frames involved in a combo are relatively static; the time difference involved in All Challenges is mostly down to making as few errors as possible (as well as some menuing).
If I've misunderstood, and you're suggesting challenge leaderboards for each character, you can find those under the Individual Level section.
