Why not just make it an option, configurable. So default would be as-is now, for the potatoes out there. But for everyone else who wants more zombies you could have them. I have seen many more Z roaming in some of the mods, especially in the wild, and I had no performance issues. I would like more too, yes, but I also understand why they have it set where it is now.
Friday can't get here quick enough(well Monday for us), we're all just nitpicking while we wait at this point. FFS people I've been getting my fix via Minecraft and I'm bored, even though the RLcraft mod made it fun again(so much death, everywhere), but that is getting old now too. Anyway, for this issue why not just leave it as it is and just add another damn option amongst the many others and put this debate to an end already, seems like a win-win for both sides.