I actually expected that to be the route taken to fix this, as it seemed like the way it was intended to work. Nevertheless, a 'chain-tractor' as a tech or module later on might be interesting.
In light of this and some more playing around with this idea, I've moved away from the concept of pure tugs and pure modules, to simply using this idea to provide 'enhancement packages' that I can add to otherwise normal ships to provide more flexibility. In my current game these are 2000-3000ton lightly armoured modules that I may attached to my normal ships as needed to provide either tanker/supply/rearming support, increase firepower, enhanced sensors, or other roles as needed. They can still act as satellites and orbital bases when needed, but this way my fleet is not dependant on them.