If you recall, Ds9 stated that creating a warp field around the station would lower it's overall mass (which allowed for thrusters to position the station at the mouth of the wormhole in a speedy manner).
This mechanism apparently takes place every time a warp field is created around the ship/station - which in effect easily explains 'jet fighter' type movements of large ships (which later on was apparently dropped for 'drama reason' - or as always - the writers forgetting (unintentionally or otherwise) what the technology can do).
That wasn't the first time that this was ever done, either. Granted, this was never specifically mentioned during TOS, but nothing in TOS is contradicted by this either (which is one of my own criteria for what elements of later series I reject and what elements I accept).
We know a couple of things about "static subspace fields," from direct in-show evidence.
1) Subspace fields can be used to reduce the "apparent mass" of objects.
This was done in TNG (to let the enterprise move a much larger object.. can't recall the episode, but Geordi put the ship's subspace field around something... I'm thinking it was an asteroid???... to let the Enterprise move it. This was a technobabble thing, but I remember that the ship was trying to divert this (asteroid) but the tractor beam was too weak and the propulsion system was too weak to do it. The argument kept being "how do we make the ship able to move an object so big and heavy" and the "aha moment" was when Geordi realized that he could make the object lighter instead. (Anyone remember what episode this was?)
This was done again in DS9, in the pilot, to allow the station to be moved dramatic distances using nothing but the "position maintaining" thruster system around the station ring perimeter. What's notable here is that, unless the wormhole was literally just a couple of light-minutes away from Bajor (which is NOT evidently the case), this also infers other characteristics of a static subspace field, which I'll bring up in a moment.
There may be other references to subspace fields reducing apparent mass, but I can't think of any.
2) The other effect that such a field has is that it increases the local "apparent speed-of-light."
We know this because the 1701-D has a subspace field generation system attached to each computer core (according to the tech manual and yes, I'm pretty sure also in-show dialogue) to allow the "optical circuits" to work FTL.
There's an interesting side-observation you can make re: this... that is, that a static subspace field is NOT the same as a "warp field," since there is no indication that the "optical computers" on the Enterprise are in any way affected by using the warp drive, is there?
These two things, along with numerous bit of (mainly, but not purely, TOS-related) info that makes no sense otherwise, lead me to conclude that you could pair a conventional newtonian "impulse drive" with such a static subspace field to "reduce the mass" of the ship (allowing very fast acceleration/deceleration with minimal actual thrust application) and to actually permit ships using "impulse" to move faster than light.
This works for DS9's relocation, if the wormhole is more than just a few light-minutes from Bajor. It works for the idea that the Romulan War was fought using "impulse-only" ships. It works for the idea that TOS shuttlecraft were "impulse-only" but still had those external nacelles (they're not "warp nacelles" but they are "subspace field nacelles") and that a TOS shuttlecraft can move FTL. It works for "Where No Man Has Gone Before" where the Enterprise, without "warp drive" capabiity, manages to make it to a star system with potential repair gear before the third generation of the ship's crew dies of old age. And on and on and on.