While you may be right re a change in govt. being the only viable option, if Israel go nuclear without having been attacked then they render themselves a pariah that will make it seem as though they have been the nmost popular country on Earth for the last fifty years. First use of nukes in a pre-emptive attack will be seen as beyond the par. I doubt even America would publically endorse this for Israel....
I agree it would be beyond the pale, but we're not talking about conventional saber-rattling, either. When the head of one nation publicly declares that another nation should be wiped off the face of the earth, the stakes have gone through the roof - especially with the backdrop of Iran's nuclear ambitions and all the wrangling going on with the U.N.
If Israel does nothing and Tehran follows through, will they receive the ultimate Darwin Award for sitting back and letting it happen with so much advance warning?