I don't know if there's a technical reason why do we have such a shitty gang plugin... Like we can't view the most powerful gangs, we can't see the list of all of the gangs at all, and we can't view gangs that all of the players are offline....
There are so many advanced plugins that are constantly working that the server does not need to add these. Yes, I agree, it would be nice to see gang rankings. However, it would require the server to load a lot more information, and as it is there are already so many lag spikes that loading up all of this information on the server would be horrible. A nice alteration to your suggestion is to have leaderboards on the forum.
And you can if we had forum leaderboards. The server does not need anymore lag. And being able to see gangs offline will cause a lot more.