With Obama's new plans to cut the force by 1/3 by 2022, and his recently signed StratPlan, those who favor the draft will get their wish. I do not favor a draft myself. It took awhile to clean up the damage done by our last draft, and having been to combat a few times, and heading back most likely, there's no way I'd want my life contingent on anyone less motivated.
To the OP, I have always been fascinated by Heinlein's model where citizenship (as simply the rights to vote and own property) was earned only through public service (not birth), not necessarily military, and anyone who wanted to serve could regardless of ability - not equal opportunity, just finding a job for which they are qualified, even if they're handicapped. This would include non-native born, and would be their sole means to citizenship. The older I get, the more attractive this becomes, and all the detractors of such a model are losing their relevance. Of course, I'd also take social institutions back from the government and leave it with churches and communities, etc. who always do it better for less. So a non-citizen born in this country would still have opportunities to succeed/fail, and reap the fruits/consequences of their actions, with a reasonable expectation of a safe and healthy environment in which to live. There are holes in that model, but I prefer them to the holes in our current model.