Images courtesy of MS Paint, so be kind to my limited abilities to modify the image!
I've also pondered that perhaps the rocket launcher itself could fire multiple MEGA darts in the same way that there's a cartridge for the ZombieStrike SledgeFire. Put 3 MEGA darts in a cartridge sized to fit in the rocket launcher place to truly make this a "Masterkey" (as most are shotgun-based). It's an idea, but I figured I'd share it whether it's true or not. It's always fun to speculate the possibilities for future Nerf products!