a few things...
there is only one major anchorage (Pearl Harbor) and 2 substantially smaller ports (in terms of anchorage space)(Hilo and Honolulu) in the Hawaiian chain extending all the way out to Midway (which with Midway and French Frigate Shoals gives you two even smaller anchorages).
There were two major (fleet) anchorages in Hawaii, Pearl Harbor and Lahaina Roads, Maui. Nagumo scouted both locations just before the attack and the first wave was prepared to go to Maui if the US battlefleet had been anchored there. Pearl Harbor was superior to Lahaina because it was a protected anchorage.
American coastal defenses and the garrison of 4 Regular Army regiments (the Hawaiian Division had just split into 2 triangular divisions in 1941, but the other two regiments weren't there yet), plus the coast defense artillery command (several forts as previously shown). Plus there is a Army National Guard regiment, an engineer regiment, several battalions of field artillery, and assorted other units. Plus sufficient Marines could be grouped together to form a couple of ad hoc battalions if they run out of aircraft and ships. So basically 4 reinforced combat brigades and while Short didn't understand airpower, he was an infantryman and did well in the Army schools prewar. Usual requirement is 3:1 to attack, so the Japanese need 12 combat brigades, plus of course even they need some logistical units.
12 brigades for a direct assault on the southern shore seems about right, but for the occupation of key positions on the outlying islands, more like 2 brigades. Since the point would be to lure in the US carriers and sink them, sending 12 brigades onto Oahu would be silly - you can't take Pearl Harbor by storm and then expect USS Hornet to come charging in from the Atlantic? No way. So you send the 2 brigades into the outlying islands, set up the blockade of Oahu. Now Hornet, Wasp, Saratoga, and Yorktown have a choice to make, right?
The best beach is right into the teeth of a US Army coast defense fort (Debussy). The North Shore in winter is known for its impressively large waves (hence the reason for surfing championships there in January), so the actual landing sights are fewer than you might think.
The surf at Oahu is determined by the prevailing winds (direction and speed) that day. In December the north shore rarely is good for landings - maybe a few days a month. The south shore usually was good, the east and west shore maybe half the time, combined, (but if one was good for a landing, the other was probably bad). The net effect is that you don't sail to Hawaii in December 1941 and just expect to land on the east coast on a given day.
Hilo has a relatively minor port in 1941, and a new airfield with limited facilities (recently expanded). It has a small garrison (as does some of the other islands like Kaui). It is also 212 miles to Honolulu to Hilo, so adding yet more distance here. There are also small ports at Kaui and Maui. Airfields are barely more than emergency airstrips other than on Oahu and Hawaii. So while taking the outlying islands would seem to provide bases, they only do if the Japanese bring the needed engineers and everything else that is required to build those bases.
Seaplanes don't need airfields.
The Army was in the process of building B-17 bases on all the major outlying islands. It is known that some of these were at least partly operational, because the B-17's at Oahu were dispersed into the outer islands after the attack (If a field can operate B-17's, the Japanese could use it for anything in their inventory.) The navy also had other fields, (such as Puunene) that could operate a carrier wing. Various civilian fields suitable for the lighter aircraft the Japanese flew, (a Zero does not need the takeoff room of a B-17).
The IJA doesn't have 12 combat brigades to spare (4 divisions basically), nor a spare field army headquarters to support them (and two divisions normally is a Japanese Field Army, not 4). The Navy doesn't have the transport fleet to move them unless the Philippines and Malaya operations are cancelled (which is where all the transports are for this size a lift).
Malaya could have proceeded, Philippines could not have.
It would take an enormous amount of oil to fuel all these ships, plus their escorts, plus the battleships needed for the fire support force (one per division would be reasonable plus their escorts too). In effect, it would take the entire fleet that moved on Midway Island, including all the carriers, and every available tanker and transport.
Figure on at least a million tons of fuel spent for a Hawaii campaign. Maybe even two.
Which means at best the Japanese hold Hawaii but don't have anything else.
So if the Americans were defeated at Hawaii and thrown back to California, the Dutch are then going to hold the Japanese back with a cease and desist order or something? Gandalf sitting on the beach at Java wielding his staff, shoutin, "
you shall not pass!"?
The majority of food for the military and civilian population has to be imported in 1941. No wheat, damn little rice, and while there is plenty of tropical fruit for a short time that is a short term solution. No oil, no coal, and some islands don't even have all that much in the way of forest so firewood is an issue. No medical supplies, spares etc... the list goes on and on
So everything pretty much has to be imported, and from a distance twice as far from Hawaii as North America is.
Correct, Oahu was extremely vulnerable to siege tactics.
If the Japanese could somehow take it they couldn't do anything else. The Army would never agree and the Navy could never support it. It would take a huge chunk of the Japanese merchant marine just to keep a garrison supplied even if the outer island strategy is used and no immediate attempt is made on Oahu.
One of the factions arguing against Hawaii used that tact, which was that Hawaii would require about 30 supply ships, (180,000 tons) supply per month of the civilian population. That worked out to 6,000 tons per day for about 500,000 people, or 24lbs per person per day. A realistic figure might have been 1lbs per person per day support, about 2 supply ships per month.