Yay, it works! The cloning and compilation of the theme takes a lot more time than you might expect, so please be patient while it does that …
So, here is the repository: https://github.com/pojntfx/adwaita-icon-theme!
Be sure to turn of Night Light/Redshift in System Settings etc., otherwise the colors could be different from what you might expect!
Some screenshots:
First of all, Ambiance and it’s icons for comparison:
Second, Adwaita-GTK-Ubuntu and Adwaita-Icons-Ubuntu:
Light:
Dark:
On the subject of the shell theme: Ubuntu 17.10 comes with a near stock Adwaita shell theme that people really seemed to like (Especially the transparency!). I do actually not think we have to do any changes to it if the colors would be orange, and if they would be blue it would also be very simple as the _colors.scss file is the only thing that would need to be changed - it’s nearly the same as in Adwaita-GTK-Ubuntu! Forking Adwaita however would be a simple thing as well - I don’t like Ambiance’s headerbar to much 
What do you guys think?