How about adding the 5.1 difficulty or doing whatever (classic mode, all-star, etc.) with all the characters or something like this.
For example I want to do a speedrun of classic mode 5.1 or 5.0 (i just don't care) with all the characters (no DLC and 3 miis, one for each type)
Problem is we already have lots of dead category's and if its just gonna one or two people running it I don't see the point in making another category. If you can find a good sized group of players who would like to run it then I'd be more than happy to add it.
Most likely not going to be adding more categories that'll accumulate more runs on the board with no video evidence. Generally when asking for a category it'd be best to provide a run of it first as well to show interest rather than claiming interest because a lot of the time people will claim interest and not actually act upon it when a moderator makes the category. Still though, unless there's overwhelming agreement with proof of interest, there won't be more categories because of the high potential of few runners on top of no video evidence making it kind of pointless to track.
