I had pitched a similar idea here on HN a few years ago, and have recently done some more design. Rather than "bubbles", I would have a robot go capture metallic asteroids, and use them as the raw material to build a sun screen. I personally cannot think of any viable alternative to building some kind of sun screen at L1.
My new design envisions a robot spider which basically weaves a web.
Build out renewables. Displace fossil fuel burning. Unblock capital for building out renewables. Stop subsidizing fossil fuel extraction. Tax fossil fuel extraction and burning, and use the money to subsidize build-out. Outlaw fossil fuel burning where taxes would not suffice.
My new design envisions a robot spider which basically weaves a web.