I'd love the windows 2000 style classic theme with the overall customizability improvements in XP with the UI feature sets of newer versions.
E.g. booting up 2000 by itself it absolutely sucks. I mean, it looks great... but you can't tile windows, you can't resize the command prompt dynamically, you don't have DPI support, a lot of the little victories like pinning and grouping aren't there, the way it draws often causes ghost trails, virtual desktops aren't a thing, a surprising number of things were modal when they didn't need to be. It has great parts but the problem isn't newer versions threw them all away with no improvement it's that not every change was an improvement.
E.g. booting up 2000 by itself it absolutely sucks. I mean, it looks great... but you can't tile windows, you can't resize the command prompt dynamically, you don't have DPI support, a lot of the little victories like pinning and grouping aren't there, the way it draws often causes ghost trails, virtual desktops aren't a thing, a surprising number of things were modal when they didn't need to be. It has great parts but the problem isn't newer versions threw them all away with no improvement it's that not every change was an improvement.