There are many other ways to achieve these goals that don't involve mandatory military service, and the benefits of these don't outweigh the costs, risks, not to mention loss of human liberty.
That liberty is only made possible by those willing to step up and do their civic duty.
If there is going to be a 'service' and there has to be in 2019, then it makes much better sense for everyone to serve.
The issues, to me are when we get into 'unneeded' interventions etc..
Perhaps people could 'chose their corps', because there'd surely be a lot of medics, non-combat Engineers, IT etc. volunteers.
Sweden, notably one of the most socialist countries on the planet does this out of obvious necessity: Russian on their doorstep. They stopped mandatory service and then re-started it again.
"and the benefits of these don't outweigh the costs, risks"
What costs and risks? To you? Or to the nation? It might actually be a lot cheaper. And I don't see any endemic risks in having everyone serve a couple of years.