I'm glad everyone can agree on an alternative to the original idea, and I think it's more on-the-mark than, "VIP for forum popularity".
As everyone stated earlier, VIP for forum stuff just doesn't work. VIPs are VIPs because they help/have helped the community on a direct basis, be it through moderation, advertisement, or creation. Forum members do so on a less direct route, assisting and bettering players who are already involved with our community (I consider owning a forum account as a significant step in being part of MCGamer's larger community and culture). There's no question that they are influential and appreciated, but their assistance may not warrant such a generous privilege. It's, "bringing in new people" versus, "helping the ones who are here now".
But for that reason, I've been trying to find non-rank-related ways to encourage good posts and great posters. There are three new forum trophies that were added in (Positive Poster, Power Poster, and Profound Poster) that measures Like/Message ratio after 20 posts or so, thus encouraging people to make thoughtful posts. I was hoping to do something with the Medals system too, though that's still very much WIP. I'd also like to have some unlockable forum abilities as well, like text colors or fonts, but I do not believe Xenforo will allow us to do so; there are no options to configure the text editor with rank/trophy/medal-specific functions.
If anyone knows of anything else we can do, I'm all ears.