I know it's already been stated, but the simplest "fix" for Rival Wings would be to add a Daily Roulette/Challenge for it like the one that already exists for Frontlines. That alone would bring in tons of new blood to the game mode. I'm not saying other changes like the ones posted above aren't necessary, just that the fastest (and seemingly easiest) way to revive Rival Wings' population would be to add a lucrative daily incentive to players who would otherwise probably not even play it.