That could definitely help. However, while I don't have the numbers, I'd expect that the required labor to disconnect them all would vastly exceed the 24-72 hour warning time.

Also, this would mean proactively shutting down the entire grid for days, at the first warning, then requiring days to restore power. So one warning would require a full week of zero power for the continent, and (I expect) saving only part of the grid.

But yeah, putting in some planning to do that would be a smart idea.

Part of the challenge is that transformers for individual homes are at risk. Throw a significant DC voltage across a transformer designed to handle 60 Hz AC, and the results are not going to be pretty.