After your level 300, after you have huge storage reserves, About the time your building an enormous base, you may want to stop fighting the hordes. This base allows for just that. It is high enough above the ground that cops won't hit it. The main idea is to be high enough so the cops can't get to you and the supports are safe from the zombies.
All of this allows you to save your time and resources. no more shooting hundreds of bullets and replacing them for the next horde. No more repairing blade traps or electric traps. Spikes Ha! they cost too much and are pointless in a17.
I have Incorporated a fall pit to help thin them out the zombies below. there is a set of ladders below to help the zombies path up. Changes should include a ramp in case there are dogs and bears.
This will also help in case ferals, cops and wights break some of the ladders.
Things on the upper platform you may want to add are turrets for dealing with vultures
Your other option is to drive around the world and just do that every horde night, its up to you.
Interesting, I am not familiar with this game. Is it a very new one?