Not just military service they are talking about.
2 years military is one option, the other is civilian service.
So long as civilian service has a broad range, i don't have a problem with it, and am in favor of it.
Consider anything related to fire, rescue, medical, and law enforcement to be included. Consider workers in the education system. Those that keep utilities operating in emergencies and bad weather.
Coast Guard. Those that fight forest fires. Part time and volunteer firemen, paramedics, and so forth. WWII often exempted oil workers and farmers from service, as these were strategic needs.
Part-time national service could be volunteering to clean up trash, or be involved with building homes for homeless. No end to the kinds of volunteer work.
You put in your time. All at once, or a little at a time until you meet your commitment.