The current ranking is perfect, based on gamification principles. People want to get on the list because of renown, and they want to do better, as it's not only time based - it's time and skill based. Both things are good for the game, and current raking worked well for a long time.
If you want to add a ranking, it should be a new one. The only other reasonable one I know is ELO-based (chess), where you get more points for sinking someone with your rank or better. NA is different than chess though, as it's not always a 1 vs 1 game. This would also need to be included in such a rank - you should have no points for ganking a same rank player, and much less points if you have a higher rank already.
WIth such ranking, you would have a few advantages:
additional progression goals for players
incentive to fight non-gank fights. Since they're more fun for everyone, it's good for the game
option to reward more for sinking renowned players much higher than you, which would empower new players as well
If GameLabs made such a ranking with a help of a mathematician, it could be a great addition.