I haven't heard the second theory advocated before as the primary explanation for the war. As such it does seem to satisfy the conditions for being a conspiracy theory. But if one is merely asserting that this was one of the many possible contingencies that were being planned for, then I disagree that it requires the government's motives to be different from what they claimed and so I disagree that it's a conspiracy theory. They are open about wanting regime change in other states, and open in refusing to rule out pre-emptive force if they deem a regime to be a threat. Obviously, once it was decided that Iraq should be next after Afghanistan, any such contingency plans would involve using Iraq as a base.

Under the interpretation where it is a conspiracy theory, it is a much less severe one than the oil theory, because it involves coordination among only a handful of people (in principle, it need not be a conspiracy at all: the President could be the only conspirator), it involves no spoils and therefore no coordination over them, and also because the purported motives and moral values would be very close to the conspirators' allegedly actual motives and values.