Now you brought up something interesting. Should a person be granted full citizenship if they reject conscription for any reason? As was brought up in the story "Starship Troopers" by Robert A. Heinlein.
In the story, those who refused conscription for what ever reason paid higher income taxes were sort of second class citizens. no voting rights, families regulated as to how many children but otherwise lived pretty normal lives. Something like this I would worry about, not creating boogey men all the time. The only reason the story was news worthy was that it hadn't happened since the cold war ended.
Interesting. Shari'a has something similar. Muslims must pay a tythe of 1/40 of their income to the poor, whereas non-Muslims must pay 2/40. However, in the event of war, Muslims must join the fight whereas non-Muslims are free from that obligation, and if a local non-Muslim community can't afford to build their own church or synagogue, the state provides the funds for its construction.