[aurizon]

The use of combustion based propulsion is doomed IMHO, except for imminent collisions that warrant a rush launch of a mobile, attachable thruster. My preference would be the perfection of a number of attachable(glue or epoxy or clampable?) ion jets with a suitable steerable solar cell to power it along with a refillable mother ship with a dozen of these deployable systems within it - perhaps in a standard large cube sat that is large enough to boost and refill the mother ship - which would have it's own solar array to power it's own ion jets to meet the prey to be de-orbited. Once there the small de-orbiter would be released close to the prey, whereon it would deploy it's own solar array and steerable ion jet system (which might be a set of 3 for steering. I agree, their thrust would be low - but continuously applied until depleted it would act to lower the prey to a higher drag orbit. In addition, I might suggest that all satellites be designed with a number of standard push-on attachment fittings, perhaps with orientation ridges(to prevent rotation) alongside so one of these thrusters could attach and lock to the prong without need of glue or threads. I am sure that such an attachment prong can be designed. There are fairly frequent cube-sat launches that could, for a fee, be willing to orbit more of these thrust recharge cube sats to add to the fleet that is gradually going to solve this issues.