I can't believe I've spent twelve hours dicking around with this and have now arrived at what is probably the simplest solution.
It turns out that a single jump inhibitor module will give about 10,000 points of jump drain effect (just how much that really is, I haven't a clue). To simply double that effect takes vastly more inhibitor modules and vastly more power. Clearly, many small effects each on a separate ship is the way to go. Well, it so happens that my drone fleet contains many small ships. So... Put a single module jump inhibitor system on each ship. Install a sensor with a two block clock that detects if the shields are at anything less than 100% and if so, activate the inhibitor. Thanks
Malacodor. (I just hope this doesn't cause too much lag in so many drones.)
A mere handful of blocks, a small power cost of which my drones had sufficient to spare, and now I have a plethora of inhibitor fields potentially going, many of which will very likely at least occasionally be drifting within range. It would probably still be a good idea to have that dozen or so inhibitor 'torpedoes', just to be absolutely certain to quickly nail a chain drive.