Speaking of codex craft, my overall experience with the gold codex goes somewhat like this:
The hawk could use a slight buff, maybe, damn thing is fast, sure, but basically serves no purpose since you can't really do anything with all that speed. The range is too short to be used as troop transport for anything much beyond double the the HWD range (which isn't exactly a small area, but much shorter then pretty much any other craft), it doesnt make a good interceptor since its really fragile AND takes a good while to repair AND is one of, if not the most expensive codex craft. I'm kinda on the edge about this one though, since to me it looks like one of those craft that really need you to stuff the right STC into it to become useful, and I haven't got to the point I can actualy craft STC yet, though by that time I'll probably have vessels that fill every role better than the hawk, so I don't see much of a point for the hawk atm.
The turtle is a pretty useful troop transport, and despite being so slow, its still way, way better than the skyranger merely for the fact it has actual doors, has pretty decent layout, and can go underwater. The three STC slots are intriguing, and could be used to maybe increase its speed and make it even better.
The shadowbat is the shadowbat, IE, its pretty great, though I do miss the conversion launcher.
I never actualy used the jellyfish so I can't give an opinion on it. I always saw the snake as the better choice, since not only can it go underwater, its also a pretty decent troop transport and decent interceptor.