i would like a consistent gradient hill that could be used to maximize my FTP test (and maybe make it slightly more bearable). I am so much more motivated when I have a physical goal in sight (i.e. - getting to a summit peak) so if Zwift had a 20 minute climb specifically for this purpose, I would be more inclined to do regular FTP trials and probably even do better on them.
You are probably thinking everybody is different and we would need many different hills to satisfy everyone’s fitness level, but my thought is that it could be handled pretty well with the trainer difficulty slider. At a given incline and total distance to the top, the slider position would determine the average w/kg needed to reach the summit in 20 minutes. So in designing the route, the “real” distance and climb could be determined such that a reasonable range of rider w/kg could be accommodated within the range of the difficulty slider.
It is possible that I missed something obvious in my technical understanding of the trainer difficulty slider, and I am sure someone will point it out to me.