The history of the Colonies doesn't lend itself to limited warfare, and for that to change it will need a Year Zero moment. Lukon likely has the military strength to achieve that and Valakyrie's scheme presents a way of doing that which would inject some new life into the island.
Such a war is in any event unavoidable as Lukon naturally seeks to remain engaged whilst the number of realms she can war diminishes.
Neither the Assassins or Minas Thalion have the wherewithal to provide good sport due to the poverty of the north and their lack of capital cities. Therefore war with Oritolon and Outer Tilog are the logical steps IC with it likely at the bare minimum that OT city and Alebad will fall within weeks of first assault.
Perhaps if the two realms worked together they might hold their own. However I don't see that happening given their mutual history of avoiding conflict with Lukon. That ship sailed a long time ago.
