I served in civil defence and can say that that's definitely a good idea as civil defence relies on a large reserve. While getting volunteers once shit hits the fan is absurdly easy, practically none of them can be taken on, at least not for tasks more complex than forming a human chain to move sandbags, because there's no time to train them. When the draft was still active there was a steady trickle of conscious objectors, and even if they don't serve in the active reserve they're still people you can integrate quickly. It hasn't been that long since the draft got suspended so readiness isn't in dire straits but if it goes on, it very well could be.

A couple of months on how to operate a radio, structure and organisation of the services, some theory about dikes and floods or avalanches or whatever might be applicable, qualification as a low-rank paramedic, knowing how to evacuate a city and build a tent city and operate goulash cannons never hurt anyone. Heck, half of that is a summer camp. A year would be a bit much I think, six months would be adequate, but there's nothing stopping different services from requiring longer service. Civil defence is a good place to put people who can't be arsed to choose though, I think, and it'd be cheap and easy to expand training capacity to cover a complete cohort. We do have a fuckton of tents and goulash cannons, wouldn't hurt to actually use them.

Also, just like back in my days, don't require people to do the service in one continuous block, mine amounted to an average of a weekend per month for five years.