Difficulty might be a good idea, but unless someone has serious intention of running it, there' no point in adding the option for it just to stay empty. I'm sure if someone posts a hard/maniac run the mods would consider it.

Level leaderboards wouldn't make sense in this game (or any Fire Emblem game) because you could spend as much time as you want grinding the previous chapters until your characters get maxed out, making the runs irrelevant. It would sorta be like a Pokémon Gym IL, where you have level 100 pokes.