I think it's a bad idea, but I can see the merits of it if you make that an even amount of time for either. Making the military a quicker path to reaching citizenship is a bad idea in my mind. However if you did have to run with this idea the evenness would also expand the other way, just because you choose to do domestic work doesn't mean you will have more free time than in the military, you could get sent out to the middle of nowhere to do something like road building (on stolen farmers land ) like you say.