I'll define a better scenario (realistically speaking)
An Arstotzkan ICBM lands in Rhinestone's EEZ. We will take this as a sign of war. Since Arizelon and Rhinestone signed a MDP, we will both militarily help each other.
Arstotzka ignores the sanctions, more tests still occur. This will force Rhinestone to intervene.
Svostine and UHAE will most likely intervene with Rhinestone's cause. As for Valkyrie Union, I don't know what will happen.
Try making a story out of this scenario