I kinda feel like that 'safest' option, even when including the 'no nukes' option, is for stable and rational powers to have lots of nukes, and probably a 'fail-deadly' doomsday machine type setup. If they're all rational, and all know about each other's doomsday machines/deadman's switch, they wouldn't attack each other as it would be tantamount to suicide.

Of course, things start to get a bit dicey when you add not so rational nuclear powers in to the mix (e.g. North Korea), or diversion of nuclear bombs to not so rational 'non-state actors'.