Earlier quoted context omitted.
Unity was a great project, but not all is lost. I've been using this GNOME extension for years, and it's been very solid: https://extensions.gnome.org/extension/1287/unite/ It emulates Unity quite well (removing the titlebars on maximized windows, among other things).
It only provides some of the cosmetic look of Unity. It doesn't provide any of the functionality, such as global menu bars, keyboard controls, a dock with both keyboard and mouse controls, and so on.
But at least some of the things you enumerated should be possible to add. Maybe file an issue, see what happens.