Yep Zombies are the next big threat I'm positive.
I like where you're going but the G-Wagon would be a poor choice in a Zombie Apocalypse imo. I mean you'd only need to try to run over 10 or 12 Zombies at once and it'd probably ground the wagon to a halt.
My FV150 Warrior however would not have such a problem ~ it weighs in at around 25ton, is a tracked vehicle, has a 30mm cannon for long distance Zombie destruction and can carry 10 people in all including the driver.