Countries without a strong nuclear deterrence don't have a seat at the table in this new geopolitical era. Looking at you, Ukraine, Taiwan and (can't believe I'm saying this) Denmark.
https://bilder.deutschlandfunk.de/72/d7/aa/c5/72d7aac5-be14-...
https://media.cnn.com/api/v1/images/stellar/prod/17070508372...
France has a first-strike doctrine. It's unique in the world, and it scares the shit out of everybody. An EU arsenal would be a typical retaliatory-strike doctrine.
In every war, eventually, one side will be about to lose.
It is still risky of course and not advisable.
It works as long as the harm that can be threatened is sufficient to outweigh any perceived gain of winning. Small states may not be able to sustain as large of an arsenal, but they also rarely offer as much value to a victor.