As pointed out, the idea about drop tanks seems to have issues, but why not examine the practice to see what is involved?
What happens when we have an enemy fighter of 10 dTons nearby when a ship attempts to jump away? Anything? Ok, let's turn it into a 40 dTon boat instead of even a 50 dTon cutter? Exactly how far away does a drop tank need to be before it is no longer an issue? Can a 5,000 dTon destroyer inhibit any other ship's jump just by being within some arbitrary zone of distance of the jumping ship?
Let's say that we have satisfactory answers to all of that - the laws of physics are such that we can estimate the force required to move a given mass a given distance. It shouldn't be all that difficult to either confirm the possibilities as viable or not right? But let's take a moment to think outside the box...
What if those tanks, instead of being propelled by explosive bolts, was instead, powered by battery powered reactionless motors instead? What if the tanks were made with bonded superdense material instead of cheap materials? What if, to borrow another aviation metaphor, we used a drogue like approach and used a high pressure fuel hose to feed into a specially designed fuel intake valve and permit the fuel tanker to cut the line just as the jumping ship is accelerating away for its jump? In other words, the jumping ship need only be outside the so called danger zone when it finally jumps.
CT concepts have evolved over time. It used to be that there was only the entrance into Jumpspace and exit from Jumpspace that mattered. If a craft was within 100 diameters of a body, it could impact on the transition into Jumpspace. Why should anything change with the advent of drop tanks? Why not simply set the rules to where either the tanks are far enough away or they aren't?
Imagine self-propelled tanks such that they have 6G's of acceleration, contain 80% of a ship's hydrogen fuel needs to jump, and were all battery powered. No fusion power plants, no bridge requirements, no life support requirements - just boosters for jumps?
Me? I'm not a fan. But if they are to be a part of the game universe, at least make the rules internally self-consistent so that we can't build other forms of jump boosters, which is really all drop tanks are. They permit the drop tank users to temporarily increase volume without the volume being counted at the moment the ship enters Jumpspace.