Oh, I agree.It would have been far worse than that. According to Walter Lord, by 4 June 1942 the defending garrison on Eastern and Sand Islands amounted to three Marine Defense Battalions plus two Rifle Companies from another and a handful of Army and Navy personnel. These totalled about 3,500 men and were equipped with the following:
4 x 7 inch (178 mm) coastal gun
6 x 5"/38 DP
24 x 76.2 mm (3") DP
8 x 37 mm AA
18 x 20 mm AA
42 x 12.7 mm MG
30 x 7.62 mm MG
5 x M3 Stuart
1,500 x mines, booby traps, and other IEDs spread throughout the beaches, the lagoon, and the barrier reef, not to mention the handful of PT boats that the defenders still possessed.
The Midway Defense Unit, while roughly equal to a regiment in numbers, had the firepower of an entire division. The Japanese, without the benefits of American-style big gun fire support, LVTs, and the like, would have had to overcome the booby-trapped barrier reef (which is exposed at low tide), travel four to six miles over the heavily mined lagoon under the guns of the defending Americans before even hitting the beach, and then grind their way through a series of bunkers, trenches, and barbed-wire entanglements against a determined enemy on 'death ground' that they only outnumber 1.5 to 1 and with nowhere near their level of heavy equipment. In short, Col. Ichiki and his men (5,000 personnel) would have been utterly murdered a few months early; nothing less than a division-sized unit would have been adequate to seize the atoll.
I was pointing out that, even without the breaking of JN-25, the forces deployed to Midway would have made any back of the envelope, "we'll just walk right in" assault on the atoll effectively impossible.