Pakistan have provided "security" to Saudi in the past - IIRC there were stories of about 10,000 troops moved to the Kingdom about 10 years ago in a spell of tension.
AS for Nuclear weapons I'm sure that the fate of of Libya, Ukraine and now Iran means htat nyone who can will be going flat out to get a weapon. I'd see it as my duty if I was in any medium sized power that might cross the USA, China or Russia