Having the options of standing, crouching, or laying prone could provide some strategic advantages.
I am thinking mostly in regards to making it more difficult to be seen. For example if I want to go between two houses and I know there are Zs close by and wandering around, I could go prone and then crawl.
Movement speed while crouching and prone would be reduced appropriately. But at least I’m not just walking around upright like a dork 
Also crouching or laying prone behind a bush could make it even more difficult to be seen and allow one to possible loose a pursuer that relies more on sight than scent.
I do not know the best way to indicate this in the interface. Some ideas I have are:
- Display words: Standing, Crouching, Prone.
- Display letters: S, C, P.
- Display a symbol: |, /, _.
- Change the color of the @.
Thanks!