Zombie speed scaling UP in sandbox option and/or as a ramping game mode?

[Kaitel]

So I enjoy tweaking sandbox options to get the exact type of game I want, and while this is largely achieveable there is one setting missing that I feel could add a lot of late game depth.
Currently there is the decomposition option where zombies can slow and/or weaken as time passes, (which I always disable), while I can see the logic behind this, there could be a much more interesting reverse option, gameplay wise, of the zombies growing in strength and speed as they feed and "mature", eventually becoming super sprinters over a set period of time.

Now I guess some of you are thinking why not just set them to sprinters from the start, with perhaps fewer of them with numbers increasing? Yes, that is the closest alternative at the moment, but the reason to have them scale up in speed/strength is because early game you have limited weaponry and no strong base or stats/skills, so you need a chance to get established and even a few sprinters could easily overwhelm you, but late game when you're sitting on an arsenal of weapons and ammo, a strong base with multiple escape routes, vehicles and not much need to venture very far, that's when youre ready for a greater challenge, plus it adds tension, dread and incentive to get to that stage ready for the impending zombie evolution.

I see too many PZ streamers, with weapons mods and an army of super survivor NPCs inside fortress basses, while it's fun to get to that point, once you're there you have very little to fear, but this option would make for some insane late game base defense and spice things back up, because let's face it, you're not supposed to survive forever in PZ.... THIS is how you died.
 

[Fuzzy Wolfy]

The Devs have said that they're not interested in implementing "Super-zombies" or special infected, ala Left 4 Dead, but I think this is a reasonable and fairly easy thing to add—as far as coding. Like you said, it'd definitely make for a more interesting bit of ramping challenge, which the current sandbox settings don't really allow for, except for increasing numbers.

[Kaitel]

That's fair enough, I'm not asking for anything that isnt already available, just the option to ramp up instead of ramping down the difficulty as the game progresses. I just meant evolving to strong sprinters that you can already select from the start, which I termed super sprinters.