I'd like to see some form of national service reinstated, but only if it was inclusive. Under the old Selective Service law college students, medical students and others could get service deferred until they completed their education. This seemed to work. Most of my contemporaries in the '50s finished school,then served. I don't recall it stunting any careers. On the contrary it gave them a perspective on the Armed Forces that allowed them to make informed judgements about national security issues, rather than being blindly pro, or anti military, as so many are today.
I strongly disagree with the idea of some sort of "Community Service" alternative to miitary service. If that happened, we would soon see the white, suburban college kids mostly opt for the feel good "Community" option, while the black, rural and blue collar kids would end up in the Infantry, as they always have.
National service, to be democratic, must be ruthlessly fair and inclusive of everyone who is not physically or mentally unfit.
If we can't do that, it's not worth the trouble.