Is there any chance of a vehicle-scale quantum drive that will allow parasite ships like the Merlin or Argo to just spline jump around a planet or moon, but not necessarily cross the distances between planets?

It's not something we've really considered. It's not going to be a never say never thing, but those snubs have restricted ranges by design. We could definitely make it easier for them to get around places, but I don't think a vehicle size quantum drive is the answer to that.