It should also be possible to de-orbit obsolete satellites faster if they can at end-of-life deploy a "sail" that will cause more drag.

Eddy-current-generating tethers seem a more practical option:

<https://www.colorado.edu/faculty/kantha/sites/default/files/...>

(A plot point in Neal Stephenson's Seveneves.)

And then we have to consider what’s the effect of all those vapourised metals on the atmosphere