Any reason SpaceX cannot just build a giant solar shade at L1? This seems fairly doable on the decade timescale, plus it could do double duty as a weapon.

I did the math out on this for fun a couple years ago. It came put surprisingly reasonable.

Taking estimates for Starship payload to Mars as the likely payload to L1, carrying to L1 enough thin reflective mylar film to block around 0.5% of light to earth would cost between $80-100 billion. Which is a lot but not nearly as much as I expected and not outside the realm of possibility.

I love how you didn't even take a beat before suggesting that it be used as a weapon.