I'll separate the ideas in bullet points :)

* With the recent update having zombies aggro when you're close enough to them, perhaps a sandbox option to disable this feature while leaving the aggro on by default? Zombies tend to, more often than not, group up around doorways, so if you end up trying to get through them, you're immediately swarmed. If the Infected truly believe we're one of them, it wouldn't seem right for them to suddenly remember because we stepped too close to them (unless this is already a thing in the books, I haven't read them, my bad). I think the idea of trying not to be too human around them keeps the suspense alive and fun.

* Since the zombies believe we're one of them, perhaps the ability for the player to walk and move around like zombies, even so much as tripping over windows and fences with the chance of scratching ourselves? Whereas default crouching and walking would rouse "some" suspicion but not enough to set them off... though they might follow you around. You know, just to be safe. (I suggested this before in the subreddit, but I figured I post it here for the list's sake :))

* Perhaps if the nearby aggro is active by default, this could tie in with the second suggestion: In this case, shambling and behaving like a zombie up close to zombies will not aggro them.

Awesome feedback. Definitely going to take a look at these for next patch