I also would agree to public service as a condition of voting, though not limited to military service. Not everyone can serve in the military, but they can serve otherwise. Cops? Firefighters? EMT's? Doctors and nurses? What about them?
In what I see as an ideal country, all residents who desired citizenship would serve- and those that didn't would be taxed higher and receive fewer to no government benefits as a result. With those higher taxes being used to fund the citizen activities (which will in turn, benefits everyone eventually- trickle down economics at its best). Felons and repeat misdemeanors would be barred from citizenship. In short, Volunteerism writ large.
Say, just off the cuff here, you were required to serve a week a month. Same deal as guard call up- you can't be fired from your regular job (if you have one) when your time comes around. You get paid at a determined rate for your time- regardless of what you do (think jury duty here, but a real wage). You do what is needed, depending on your skills.
Your area needs repaving? Guess what the citizens will be doing this weekend. School needs fixing up? Ditto. Local park gone to crap? same. Hospital overrun with cases? that too. Bad part of town needs extra policing? yep. You might dig ditches, you might be tasked with infrastructure repair, you might watch kids so others can work, you might work in mess hall feeding the other call ups. Hell, you might even work at your regular job if that is what was needed.
In short, a social organization (ideally with a rotating membership to prevent bureaucracy from rearing its ugly head) to have people go where they are needed. Who decides what gets done? Your community, your county, possibly your state. The citizens decide what problems need to addressed and where. Not some jerk in DC. Not some nameless feds in an alphabet agency.
Something like this also partially addresses some other social issues. Unemployed citizens would get at least one week of work a month-and get fed/housed while doing so. Tansstaafl (Think the old CCC camps).
Immigrants? No issue- if they are willing to serve, willing to invest in this country, let them. If not, no help given.
This kinda thing works to some degree already on a very small scale- local barn raisings, church groups, Habitat for Humanity, some MAGS I'm sure.
To make this kinda thing work, large scale, our society would actually have to teach civics and social responsibility in schools. People would have to step up, sacrifice their precious leisure time, and show willingness to both lead and follow. People would have to invest in their society, their community, their kids and grandkids; be willing to teach what you know and be willing to learn as well.
Oh well, its nice to dream a bit