Good idea, needs work.
Specifically, the mech-suits.
The charge-up laser is worse than useless, the grenade launcher on the NEO-mech-suit uses YOUR GRENADES, which is bad, and both mechs lack a melee attack, making them unable to deal with the fast zombies. The NEO is wholy unable to deal with fast slash-zombies, and the mechsuit has to WALK all the way to the other side of the map and turn around, getting itself just barely enough time to turn around and get a few shots off before the enemy is upon them.
They're giant robotic mechanized suits. The NEO even has claws. WHY do they not have a melee attack?! I should be able to smack some zombie fools all the way across town with one bash from the heavy arms on the mech suit, and I oughta be able to just rip heads off with the NEO's manipulator claws.