Why it should be included: It provides a native adwaita theme for qt applications to look more native on Gnome without needing to use theme engines that adapt GTK themes. Or if you just really like adwaita / adwaita-dark you can just use it as the application style in Plasma and set adwaita-dark as the GTK theme.
Is it Open Source? Yes, GPLv2 / LGPLv2
Who and how many users do you anticipate will use this software? Myself and anyone else who enjoys Gnome and adwaita / adwiata-dark since it's an excellent theme. I would expect an appreciable portion of Gnome desktop users to be interested in adwaita-qt.
Link to source: https://github.com/FedoraQt/adwaita-qt/archive/1.1.1.tar.gz
I'd also volunteer to maintain the package, as I'm able to and it's something I actively enjoy using.