For ISIS to successfully engage the Saudi monarchy and overthrow the royal House of Saud and the hundreds of related Sheiks that have held power and sway over the region for nearly four centuries would be the most destabilizing event for, not only the region, but the entire world of nations and the economies of the current lead nations -- The United States of America and The European Union -- in particular. Those two superpowers, especially Europe, have allowed themselves over the course of the last century to become completely dependent on the energy exports from the Saudis and any cut-off or delay in delivery of those exports would drive the EU to its knees in a matter of weeks, if not days. The United States would fare a bit better in the long term, however, the immediate effects of such a takeover by ISIS of Saudi oil production could be just as devastating to most of North America.
Almost overnight ISIS would turn from a troublesome Islamic activist terror organization to the holder of some of the largest and richest oil property in the world. They could literally hold the fate of the entire Middle East region in the palm of their hand forcing the political will of those nation's leaders and peoples to bow to their demands and wishes, particularly as it concerns issues important to them -- Sharia Law, making their brand of Islam the only acceptable Islamic faith and with it all that that would entail as it relates to women's rights, those of more moderate and reformed thinking muslims, and especially the future of the State of Israel. We are already too familiar with the fate of Western journalists, Christians and Arabs not "fundamentalist enough."
Of course, the United States of America could never allow such a condition to exist. At least, I use to think that was the case before the current U.S. President was in office. Now, I'm not sure what could happen if what the BBC reports as a possibility would become a reality. I'm sure it would mean the U.S. and possibly several of its European allies would send their young men and women to fight along side a misogynistic monarchy that has already existed for far too long -- but exactly what would be the marching orders coming from this White House? Would it be to ensure, at any cost, that ISIS or any other terror group will not be successful in overthrowing the House of Saud? Or, would the U.S. and its allies continue with the kind of war strategy the U.S. has engaged in since the infamous Vietnam War? Wars that are never wholly won but simply and agonizedly prolonged year after year while the war machine of those nations continue fattening their proverbial wallets and the military industrial complex becomes ever more bloated?
There are valid arguments for why having some group like ISIS in charge of the Saudi oil fields is not a good thing. The greatest is how a group like ISIS would have the world oil market in their tight grip and could literally crush markets and nations by squeezing tightly on that market.
There is also the Israeli factor which cannot be ignored. The kinds of pressure an ISIS in control of the world's largest oil reserves could put on both the U.S. and the EU over its long standing support of the State of Israel could prove disastrous for the future of that tiny Jewish nation. I am of the opinion that Israel can hold its own, but that is an outlook not shared by most. The majority opinion holds that without the financial and military support from the United States of America Israel would fold like a paper napkin if the Arab world surrounding it, led by an oil rich, financially strong ISIS would crush it in a matter of days. However, Israel has too much history of exactly this kind of scenario and when the smoke has cleared Israel would still be standing. Or, as is also likely, no one would be standing as Israel would implement its own brand of the "final solution" and unleash its 'Samson Initiative' upon itself and the entire Middle East region leaving nothing behind except radioactive glass in its wake.
There are a couple of positive outcomes to consider if ISIS were to engage the House of Saud and soundly defeat it. It would force the most oil gluttonous nations (U.S., Europe) to actually develop alternate sources of energy and stop this insatiable desire for fossil fuels. That would certainly remove any economical axe over the head of the West moot. Without the demand for the Saudi oil ISIS would lose any financial leverage it could hope to have over the West. This could also force the West to invest more into the military strength and policies of its only ally in the region, the State of Israel, which would spell disaster not only to ISIS but all terror aspirants in the region.
It would also be a kind of emotionally satisfying payback for all the terrorist funding the Saudi Sheiks have been funneling into terror organizations for all these past decades. Sort of fulfilling Hillary Clinton's prophecy that "You can't expect to put snakes in your own backyard and not get bit."
The other positive factor of having ISIS in Saudi Arabia? -- They would be headquartered in one location and one or two strategic warheads could put an end to their leadership and organization once and for all. Of course, like the snakes Clinton spoke of, without severing the entire head, the tail will simply grow a new one and become a different kind threat down the road. To a government use to kicking cans down the road that may be something this President and Congress could tolerate. Leave it for the next group of inept to deal with.
In reality, there is no lasting good or sound outcome with having some group like an ISIS taking over an oil rich nation like Saudi Arabia. The House of Saud may be the devil, but it is the devil we know and, at least for now and the foreseeable future, a devil we can still manage and deal with. I can only hope that the leaders of the free world can get it together enough to recognize the threat and deal with it rightly before it is too late.