I sort of agree with you here - per icon is WAY too granular. Problem is, that a global HSV isn’t going to fix the problem that’s been presented. The issue is that the icons are hard(er) to differentiate when all the same colour & value; which is why colouring them was raised in the first place. A global HSV changes that colour/value from white to some other global, nondifferentiable colour keeping the problem.
There are two solutions to this as I see it. One I am working on (letting theme designers colour icons as they see fit) or having the icons grouped into categories and the theme setting the HSV attributes for each category. Personally, I prefer the idea of theme designers getting access to the icons themselves and doing what they see fit in graphics apps across the iconset; but I could see the point of BF devs going the category option if desired.