The VIP rewards arent super impressive if you ask most people. Many people only get it to either support the game or to avoid intercept videos.
One of the largest problems most people seem to have with the game is the inability to find that 13th cover that fits their need.
Why not have the ability for individual players to trade covers or to put them up for auction for a specific amount of iso, HP, or CP? The biggest draw for most in many online games is trading/selling. Back in the day WOW auction house was insanely crowded because it was a huge feature. Plus by removing some rewards from VIP like healing or the extra legendary and including the feature in the VIP list you could still monetize it.