not sure about this:
in a way it would look pretty cool, and as you said it could give more incentive to play the game, and also show "best x(player, fighter, sparrer etc.)", could give "something to show others"

But in other hand: we already have events and organizations, wich have an type of leaderboard and titles to members as begginer/medium/professional.

If this would be an system it would have even more problems, likely fighting to reward an "best player of the week/month/etc" in the leaderboard would increase number of rigging/farming.