Aah- the eternal quest!
A few thoughts:

: To achieve this weight I was thinking of the following:
: Using 3mm Okume rather than 4 mm
I've used 3mm doorskins for a couple of projects and they worked OK.
My local boat lumber supply has a 'lightweight' Italian plywood as well as Okume - not 'waterproof', but with epoxy coating perhaps not a big issue?
: Sheathing the boat in Carbon twill 4.7 oz. Actually I like the look
: of Carbon and the weave is very attractive and I plan varnishing
: the carbon. Will this save weight .? cost is not a factor here ,
: just weight saving
That weight of carbon (I have some here) is about the same thickness as 8-9 oz glass.
So if you are aiming for a smooth finish it might swallow quite a lot of epoxy.
: Alternatively using 4oz S Glass satin cloth on the outside , this
: would be painted with linear polyurethane.
IMO, one of the best ways of saving epoxy weight is to forego the glassy-smooth finish where possible. Make the underwater hull smooth and the rest with minimal fill coats.
Varnish (especially lower gloss) is pretty tolerant, LPU is a thin coating and shows up every little defect, so you probably 'need' to use fillers/primers, etc.

: Eliminating glassing the interior , only using glass at the seams .
Especially for under-deck and non-cockpit areas this could work, though with a multi-chine boat you'll be doing a lot of taping. It might be just as easy (and almost as light) to glass completely- ina and out- with 3.x oz E-glass.
: Making the cockpit coaming of carbon
Yes, probably lighter than plywood, but the weight does add up since most coamings have some glass laminations as well. Hand layup is never going to be as light as vacuum molded.
: Eliminating endpours
Definitely- use light softwood blocks and minimal endpours to fill any gaps.
: Judicious and careful use of resin.
Definitely. Review Ted Moores hints on using the squeegee to get that excess resin off the boat.

: Could a 30 lb weight be achieved ?
Are you putting in hatches and bulkheads?
Weighing the components like seat, backband, hatches, footpegs, etc can be interesting.

If it is just a 'day paddling' boat, you could consider using flotation bags fore and aft rather than bulkheads and hatches.
It would save some weight. George Gronseth @ Kayak Academy carries the bags to fit Mariner kayaks- they would work, or you can make your own.

Another thing to consider would be to work out a system with the rack- there are systems like the Hullavator or you could start with Hully rollers and some foam to protect the car/boat while loading.

: Opinions of contributors would be greatly appreciated.

If you can forego 'rugged', you can make a pretty light boat. (and, not to start a fight, but even a light S&G boat will be as 'rugged' for pulling up on the beach as lots of SOF boats, and they seem to work just fine).