The ratio of ship/survey sensor is a bit high. I am not sure what the best ratio of survey ship travelling to survey ship surveying should be, but I think you want them close to even.
So the same survey ship, but with 2 geosurvey sensors and no grav sensors, or vice versa, would be more efficient for that job.
I can't think of any reason why you ever want only one ship in a system. Yes, you might have slightly less efficient surveying, but you are much more likely to get the really important information home if all surveys involve a survey squadron.
I do agree that jump ships should simply carry more maintenance supplies than other ships. For two reasons, first, the consequences of a jump drive failure are much greater, and jump ships generally do not have to be as high performance, as mass concerned, as they are generally parked at a warp point. Generally.
Having more fuel efficient engines simply might not make up for the fact that they are pushing 10+ times as much mass around as a cheaper, more disposable design would be.