There's no one stopping you from making a route and running it yourself but there isn't really a reason to add a leaderboard for a run that isn't competitively ran (aka a single run being done) I know myself and at least 2 other people have ran NG+ but again isn't not really a competitively ran category so there's no need to have a board for it. Just don't let the idea of there not being a leaderboard stop you from doing a run you want to see done. Who knows, maybe if you were to try running it, other people might get interested and it could get a board some day.