In all "seriousness", the S.M.S. remind me of the following:
1. "Private military contractors" liked the ones used in Iraq and Afghanistan. The only difference the contractors are field testing their weapons. Like the private contractors, they are former members of the government formal military. In this case they alll served with UN Spacy with the apparent exception of Luca, Mikhail, & Alto. However they are still subject to the Macross government and some how arbitrarily fit into UN Spacy command. Anything else they would be pirates or bucanneers-hence all the "pirate movie theme music".
2. Historically speaking, they are all like the priates that served the Queen, Francis Drake, or the East india Company.
3. So my fues is that S.M.S. stands for "special military service" or "selective military service".