There are no arguments here. There are dreams, and then there is reality.
Yes, z-levels will be hard to implement. That's not even my point, my point is that they can be GREAT.
Z-levels are already implemented. It’s just that if you want to see other levels it looks ugly, and if you want to process all of them simultaneously it’s horribly slow. And there is simply no way around it as long as they are sticking to Linux curses and console graphics, which they do.
So, as I told you before, you can have them the way they are now, where each floor is area by itself but monsters will follow you up/down stairs like they normally do and how every single z-level was working so far without anyone complaining about it before, or you will have no above ground levels at all, ever.
When you go to missile silo, do you really care you can’t see levels above or below?
When you go into temple, do you really care you can’t throw a grenade down the stairs?