It almost seems like a shame not to park all of these satellites in one or no more than several "junkyards", probably in several orbit distances, traveling all at the same speed in close proximity with the intent of, one day, allowing "space junkers" to retrieve them, perhaps cannibalize them in orbit and then de-orbit the remaining hulk, or perhaps if the hulk has value, somehow dismantling it and returning the materials to Earth for recycling either as whole components or raw materials.
Taking it a step further, perhaps an entrepreneur could offer a satellite repair service at some point, drawing on the considerable collection of available parts to rebuild or repair a malfunctioning satellite. Such a service, say launched by one of the commercial ventures like SpaceX, might send a capsule to the nearest orbiting junkyard, retrieve parts, and then maneuver to a docking position with the malfunctioning satellite and fix it. -
There would surely be obstacles to overcome, and I'm aware that many of the components in satellites are unique to that particular machine. A different approach might be to line up several jobs to do in one orbital zone, pick the parts from the derelicts at the junkyard, repair the bad bird, and perhaps return some of the otherwise unusable but still valuable raw materials, or specific devices that are still good and could be used in new satellites to Earth.
I'm sure it would be an expensive undertaking, but so is designing, building, and launching satellites. This approach might also lead to some sort of standardization of components such that in the event of a malfunction, an identical and already in orbit part could be picked, the satellite joined with, repaired, and sent on its happy way.
Some satellites might even need refueling or new batteries so that they could continue their useful lives beyond what was originally scheduled. It seems a shame to leave a perfectly good hulk in space when all it needs is a visit from the fuel truck. :)