It's been rumoured for years that the Saudi arrangement with Pakistan was for the provision on N weapons IF they were attacked or threatened with N weapons by either Iran or Israel
As people have pointed out why buy an IRBM for an HE warhead?
The enemy tho' are realy Iran - the Saudi leadership can really see a possible "incident" involving a Shia uprising and their fraternal brothers waltzing in (nothing to with the oil of course).
Israel is an enemy but not really a likely risk to the regime - sure as hell the last thing they want is another bunch of Muslims and they already have enough issues regarding Jerusalem to want to take on Holy Places which have absolutely nothing to with Judaism