Unfortunately, we do have to keep something. You cannot put the genie back in the bottle. I do not see the need to spend billions on replacements at this present time but we will never be able to get rid of them all.
I do wonder if CERN manages to identify some new even more powerful material, whether one of the European powers might try to create it for themselves. Thus sparking a new arms race.
Nobody in Europe's got any cash.
If anyone's gonna spark an arms race it'll be the right wing mentalists in America, the Russkies, China, or some mad despot in a closed-shop country somewhere who will just throw the required obscene amounts of money at it with no regard for the consequences or the bigger picture.
I'm all for a powerful UN in principle. The problem is you need every nation to agree to it, or how can it possibly be enforced? You'd only need someone like China to pull out and who would/could stand up to them? You'd end up creating the very problem you're trying to solve.
I would envisage the UN presenting it as an idea to it's members to take away to it's countries to be voted on/ratified/told they are doing this. Bit like a Maastricht. If the countries say no, then they don't get on the global council, and they just get eyes turned upon them.
If they say yes, then their country and any future leaders know the consequences of breaching "no-brainers". Effective removal by a delegation from the council. Or deadly action against the leaders. Let's stop pissing about having countries going to war. It is only ever the leaders that decide to declare war(backed by public or not). And so it is the leaders that should pay the ultimate price; not the civillians.
At the risk of going a step too far into esoterica, perhaps it's that very conflict within each of us that defines who we are, and if it were resolved we'd actually be nothing? Great things (and great people) often come from great adversity & great struggle.
I'm only asking try to eradicate the big red button and any future development of planet killers.
Sadly, I can't see that ever happening. Pandora's box was opened and it'll never be shut again. Imagine all the nuclear countries in the world all agreeing to destroy their stockpiles. Would you trust them all to keep their word? I wouldn't. And if I was in charge of a country with nukes, I'd say I'd destroyed them and then keep a few back for a rainy day, just like all the other leaders would.