That video's mesmerizing! I actually have a redneck version of this at home for my birds to fly in; right now, we don't let our quaker parrot out because it's too cold, but our dove and pigeon don't mind the weather.
Actually, we've been considering for the last few months buying
this house on the Costa Blanca in Spain since I've gotten a job I can do from home (I have gotten somehow much more productive since I began working with a bird on my shoulder!) and I think that building an outside flying space for our birds could be something good. Plus, the climate there would be much, MUCH better for our little Molniya, since we have to come up with makeshift measures for her to be okay during winter here.
So, if you had the choice, what would you do for your birds to enjoy some fresh air? Would it e better to build a chain-link flying space, to have them fly semi-freely with bird harnesses, or to go for another solution? So far, nothing's already built, so all options are open.