PMCs are the obvious form for irregular forces to be used abroad, Sivkov suggests; but because of their high cost, the Russian government cannot afford to have them play a major role in domestic defense. Consequently, it must look elsewhere. The most obvious candidates for that are territorial defense units including Cossacks.
If Moscow chooses to go in that direction, Sivkov says, it would mean “the restoration in Russia of a real Cossackry, a specific warrior people who would become a reliable support for the state and government under the most critical conditions;” and these could play both defensive and hybrid aggressive roles.
Such settlements have a long and storied history in tsarist times. Sometimes they were referred to as stanitsas, at others as forts, and in still a third as lines. In general, they were organized by the state so that Cossacks could provide defense or the basis of expansion along the borders of the Russian Empire.
(For background on this phenomenon, see in particular Philip Longworth’s The Cossacks (London, 1971).