I’ve had an idea about a cleanup mini-sat that’d just have to get close to debris, then fire a squirt of some kind of gas (heading in the opposite direction, natch) such that the debris would hit the gas and lose enough velocity that it’d wind up falling out of orbit (or at least start spiraling downward). The gas would disperse, so it wouldn’t be a long-term threat at all.
It’s probable, however, that the gas would disperse too quickly, or wouldn’t slow the debris enough to make it worthwhile, or it’d be too hard for the cleanup sat to get close enough with enough accuracy. Ahwell.