With all due respect of course, but this is a different approach than what has been done for the GNOME Shell Theme.
Just like with the Shell Theme, I think there should be a sense of urgency with the GTK Theme as well.
A modern looking GTK2 and GTK3 theme that has light and dark variants (dark for Totem for instance) is long overdue. Moreover, there already are good themes to start working from.
Why not just think about switching to Arc, United GNOME or Adwaita, after which we can start tweaking the colours, etc.?
Same goes for the Icon Theme. Adwaita is modern, ready, complete, upstream GNOME. Why not take the leap?
This is my opinion of course, but I would strongly suggest to reconsider.