New setting to tune zombie respawn

[Mastermindx]

There's currently only 2 settings for respawn.  On/Off.  With it off, you can end up with a pretty empty world. With it on, it can feel as though all the zombie killing was for nothing. What I would enjoy is a tradeoff between the two.

 

What I would like is a setting that modify the maximum zombie population based on the number of zombies killed so far, so that, as you kill more and more zombies, most do respawn, but gradually, the density goes down over time. Playing in a graph app, I came up with a formula in the following form.

 

Now, I'm not attached to the actual values in the formula, or the formula itself.  It's just to illustrate what I had in mind.