I feel like a lot of peacoats, and even more so whatever you call those grandmotherly women's overshirts that drape and don't have buttons, are really close to this already.

Also, of course, traditional Arab clothing, like hijab. Light, really flowy, and complete with hood or a scarf that serves the same purpose. I know Muslim women who look way more comfortable than anyone else in the summer.

Or pants or shorts plus a windbreaker, or a poncho.

Tldr: I agree, they can be practical; they just also potentially make you look nerdy or edgelordy compared to existing and socially accepted similar options, depending on how well you coordinate the outfit and such.

It might be hard to make one equally practical to similar options as well, honestly. With a light jacket, you can take the jacket off easily and drape it over something, or tie it around your waist. But a light cloak might be more difficult to make while preserving the aesthetic you want, since it's more material all in one piece, and lighter material might flap around or tangle in the wind goofily instead of flaring dramatically? Maybe if you weighted it just at the end, and more toward the center than the edges? I wonder how costume departments do it for movies.