I would like this as well, but make it a double edged sword/flamethrower. Say if you set up a campfire/firewall outside of town, the zombies will walk in it and catch fire, SLOWLY dying (like maybe 5 mins for a 'full health' zombie or whatever they're calling it). A zombie on fire could catch other zombies/players on fire (player on fire would take much more damage than a zombie, literally have to drop and roll or be near water, zombie bumping into other zombies have chance of spreading fire, chance of catching on fire when attacked). Could be a good way to clear out a section of a town at night, however any/most loot on zombies would be lost/destroyed by the fire (bullets explode, cans of food become charred, possibly still usable, flares/painkillers/ect burn up).