- "And even at GEO, there could be a debris cloud as well causing issues, at least until the sun and moon gravity perturbs it enough."

Not a satellite expert, but I understand GEO clears out relatively fast (~decades), because of those 3-body perturbations,

https://www.agi.com/blog/2020/07/geo-satellites-don-t-decay-...

Your link talks about how this is an unexpected result, and only occurs at specific inclinations.

It's new information to me, though. Thank you.

On the other hand, there is just so much less stuff up there, as reaching that orbit is much more expensive in terms of energy expenditure, and it's all moving in pretty much the same direction and in the same orbital plane.

So unless somebody maliciously launches e.g. a bunch of ball bearings in the same orbital plane but opposite direction, the chances of "wrecking GEO" seem much lower (although the consequences would, as you say, probably be much more severe and long-term).

The approximate-GEO belt involves far fewer satellites than projected megaconstellations, in a far larger volume of space, travelling at far lower orbital velocities, with a much tighter orbital plane distribution (so even lower relative velocities). Their orbital planes intersect every 12 hours instead of every 0.75 hours.

Targeted space junk disposal in GSOs appears to be quite practical. The easiest major orbital changes for an SEP stage to burn, structurally, involve lowering periapsis from high orbit.