It is a fact that we could launch light sails, and even heat up Mars a bit. The idea might be silly, but at least it is thinking big. Some other big idea will be better, including several of those listed after the light-sails bit.
The earth-sized radio telescope made out of Starlink transceivers is an obvious winner. Total coverage ground radar using the transceiver antenna is another.
If we did, it would still work better to just use it here on some isolated land.