Sorry. It's difficult to keep track of all the posts in all the threads sometimes.
Well, I took the time to explain how difficult it would be to build a system that does all the work outside of Earth's atmosphere, without requiring the use of Earth resources and energy, i.e. sending people, parts, and fuel up all the time. You would have to find some energy source outside Earth and then if you used that energy and resources to build so many solar shields and put there around Earth in orbit, you'd have a massive quantity of material that would be breaking down into space junk and falling to Earth. Maintaining a shield like that century after century would cause problems.
Basically it would boil down to using energy from the asteroids to move asteroid-mined material into Earth orbit and then weathering/erosion (yes, I know there's no rain in orbit, but there is solar wind and other energy that will cause those solar shields to break down into debris and then rain down to Earth with the force of gravity), that weathering an erosion over centuries and millennia of time are going to pollute the Earth with a lot more meteorite-type metals than would already be burning up in the atmosphere during that time.
Like most all geoengineering projects, the entropy of the artificial mechanical system breaking down and/or being maintained through time results in environmental consequences that aren't manageable.
You have to understand that organic life and ecosystems have evolved on Earth to manage their own entropy/waste and use it to maintain sustainable ecosystems. Trees, plants, and animals use latent heat from the environment to keep their cells warm, so that the nano-processes going on at the cellular level can perform useful labor with that energy.
When humans build machines that run on fossil fuel, nuclear fuel, or even renewable sources; the waste heat as well as the other types of waste generated have to be taken up and used by living organisms/ecosystems, which recycle them in a sustainable way, unlike human/artificial forms of recycling that just prolong the process of materials like plastic and paper breaking down by using artificial energy instead of latent heat from the environment.
So we really need to grasp and accept that natural/living systems have evolved to adapt most successfully to a balanced Earth-sun system, and while we can and should use industrial ingenuity to accomplish certain things that can't be accomplished using natural/living systems exclusively, we should really minimize that artificial kind of industry/engineering because it does not work very well with the natural/living ecosystems that have to clean up after it and keep the Earth sustainable for hundreds/thousands of millennia into the future before the sun really starts heating things up.
I don't see what is unsustainable about doing this. It may be a large undertaking. But humanity is capable of large projects.
You have to look at what it would take to build it and then maintain it millennium upon millennium, and what the energy input would be; and what forms of waste/output would occur.
Not doing it, on the other hand, is highly unsustainable. Life comes to an end on Earth if we don't do it.
Well, life could evolve to adapt to the changing environment, but if it did, it would be very different after such drastic changes occurred.
Ideas such as yours shouldn't be discarded without study. They just shouldn't be promoted in the way that so many ideas get promoted, i.e. because they would create loads of jobs, contracts, and stimulate economic growth. Humans tend to think less critically when there's hope of making money. They like to go with the flow and collect the cash.
All I'm trying to say is that whatever industrial projects we consider undertaking, either on Earth or outside of Earth, should all be scrutinized in terms of how they interact with a sustainable Earth where Earth's natural patterns are protected as much as possible. We should assume that Earth is healthy when left to its own nature, and thus deviate as little as possible from what Earth would be like without human ingenuity.