Things that have come up are deployment times, overhaul times and bug eyed monsters.
I have found (possibly due to astorography) that my survey forces spend a considerable amount of time and fuel getting out to the frontier. This means they burn a good chunck of fuel before they even can start survey work. Also the deployments are generally 5+ years including at least one refueling and re-supply break. A 5 year deployment for an armed ship is brutal on its systems and would require a very extensive maintenace overhaul at the end but the chance of encountering the bug eyed monsters and not detecting them far enough out to avoid loss of a ship is also not good.
For the Draak I am still trying to formulate a plan to deal with this. I have 45 known and 25 surveyed systems with the frontier now about 4 jumps out from the homeworld (or more in some cases). From what I can see part of your survey strategy has to be the establishement of forward operating bases with fuel and maintence facilities. This makes both the sorium processing module and maintenance module potentially more valuable then they seem first off. Otherwise you burn a lot of fuel simply getting your ships back to where you can overhaul them. In addition the time to fly back home is added to the clock on the ship so it prolongs the maintenance time.
It might be possible to invest in technological solutions: maintenance modules, sorium processing modules and asteroid mining modules would allow for a fleet to set up shop and process the materials needed to keep the survey ships operational longer and allow insitu overhauls (potentially at more frequent intervals).
It is clear that you need to probe the system, leaving a ship at the entrance jump point simply to ensure you don't end up with the whole survey force destroyed. But this hardly seems to a major time or fuel constraint. And as Kurt has observed even a fairly modest amount of survey ships can explore an area of space it will take decades to exploit.
The bug eyed monster question; however, is not so easy to answer. Although you can use non-jump warships this leaves them vulurable to being stranded, its hard to judge the value of a jump versus non-jump escort. I prefer all jump capable ships for survey but its obvious you gain. The other question is what sort of force level do you want? Or put another way what do you want the escort to accomplish beyond getting killed in a hopeless battle. Does it make sense to include a sizable battle group of what ends up being a very long term deployment? You have to factor in colliers and tankers as well if you are a missile using race and still the question comes up: what is the mission of this force?
I find it difficult to justify a throw away force, since if it ever gets used it will get lost anyway and accomplish nothing of significance. I'd rather loose the odd probe survey ship as opposed to the odd probe survey ship and several warships. Equally I find it hard to justify designing and building a jump capable ship(s) and then deploying it in signficant numbers on what are mostly routine operations which put serious time on the warships maintenace clocks. The other alternative is to arm the survey ships, but it is again unclear what exactly that will accomplish unless you use the star trek model and send BBs out as "peaceful exploration vessels equiped with non-military crew" err uhm riggghhhttt. I'm not even seeing a "good" solution here, but that is because I can't figure out what I expect the survey escorts to actually accomplish.
In starfire my survey vessels were armed and had support assets to allow them to make a warp point defence which would stop anything but a serious assault...largely through the deployment of mines and IDEW to back up the survey ships. I never had to field test it though.
Gunboats look to be a viable alternative with a tender for aurora. The Draak are limited at the moment by having but a single model of jump engine, and the survey ships would need to grow to mount weapons, requiring a new model of jump engine (in the works but down the pipeline several years).
Still I think until I can answer the question of what I want the survey escort to actually accomplish it is difficult to design a force to accomplish the mission. This accurately reflects the real world reality of most modern industrial countries...
