Don't let me discourage you, but I've had difficulty designing carriers with more than 40% of their tonnage in hangars. If you want a carrier that can carry 30 survey fighters at 500 tons per fighter, that's 15,000 tons of hangar space, which by my estimation would require a 40,000-ton carrier, give or take. That's without a jump drive, by the way. All my jump-capable carriers are remarkably short on hangar space.
The multi-ship survey isn't a bad idea, in my opinion. I implement it, just in a different way: one 6000-ton jump ship, and four 6000-ton surveyors. That's less tonnage than my estimate for your carrier and fighters, and it's less trouble to get sufficient maintenance facilities to overhaul them, as well.
Even with just four surveyors I find that the systems get surveyed in a jiffy. You may find that 30 gravsurveyors is way overkill.