That was a good point on the Navy's oilers. A lack of this type of ship in any nation's navy will surely hamper the range of operations a nation can carry out.

I beg to differ, though on views that the Japanese lacked merchant shipping. What they didn't have was the capacity to replace their losses in merchant shipping.
I agree with Kai Petri's reasoning about Yamamoto's reasoning. Yamamoto knew he can't go toe-to-toe with the US for a long term fight because he already realized that his country can't match the US capacity to replace sunk ships.
If we view the Pacific as one vast desert and the strategic islands as individual oasis and sources of supply, Yamamoto's view on how to conduct the war would become clearer.
Establish small forces on the outer defensive perimeter so that any force approaching it can be interdicted. Once spotted, a larger force can be mobilized to support the small force interdicting it.
If Japan can do this successfully repeatedly, with losses at manageable levels (meaning within their resources and manpower pool to replace), then Japan stands a chance of consolidating its gains. And in the long run, Yamamoto is hoping that such a stance would make the US realize that it was too expensive to continue the war. With enough losses, the US would eventually lose its stomach for the fight.
This, I think is not a far fetched view that the Japanese took, especially when viewed with what is happening in the US today.

What the Japanese failed to properly react to was the ability of the US subs to interdict their interior defensive perimeter. Think of this subs as small ranger units or snipers straddling vital desert roads or routes between oasis or towns. This operation impeded the delivery and movement of supplies, troops, etc., thus hampering Japan's ability to consolidate its gains.

From what I've read, one of the most effective ways to defeat an enemy is to identify his strategic goals and deny or delay him in attaining his goals. In this case, Japan sought time to consolidate his conquests and established an outer defensive perimeter.
What happened was that the US sent subs and other specialized units that effectively denied Japan his first goal.
The second goal, that of an effective defensive perimeter, was denied when the US adopted an island hopping strategy.
Japan met its goal of crippling the US fleet in Hawaii and this allowed Japan to gain its conquests. However, Bataan's stubborn defense wrecked Japan's time table, thus giving the US and its allies time to recover. Had Japan met its time table, there is a possibility that the war could have taken another course. I stress again, it's only a possibility.

That's my two-cents worth. I look forward to learning what you guys think.