Thanks for those quotes Sigtrygg. I guess I rely on CT Traders and Gunboats a bit much and had overlooked those.
As far as M-0 being some kind of "space anchor", that's special pleading. Stations ARE in motion. Everything is in motion, that's how it works.
You put your station in a stable orbit, but the gravitational effects of every other damn body in the system, the pushes and pulls from every ship that docks and departs, even stuff like people walking around in the station imparts unpredictable forces on it, and it will vary in its orbit over time. That is what the zero rated drives are correcting; providing THRUST to correct the vector.
The fact that High Guard lumps in reaction drives with the M-Drives in that bit about "no great distance" shows that.
I'm quite comfortable with zero rated drives being no more than 0.1G, and SOME of them being considerably lower. That feels about right, and would be about what I'd use for a full 1% of hull one (which is a lot of machinery, really). If you want something smaller, I suggest to just build a unit for a fraction of the hull; 0.1% of hull for a 0.01G version.
Further thought, at least as far as M-0 drives go, that 1% is likely mostly there to cover the grav plates. So maybe it should remain as a minimum volume and cost. The reaction drives don't have that consideration, so a sub volume reaction drive that produces fractional thrust still works for me.
Edit: Just realised G-Plates are stated to be part of the hull cost, and you can get a cheaper hull by omitting them. So scrub that thought. Either drive might still have a minimum volume dictated by the technology, of course.