It doesn't really matter in what way Arihama is destroyed, winning is still winning and destroyed is still destroyed.
To me Arihama is just another npc like Bradley. Bradley is all hyped up to be an undefeatable warlord with a pirate army and like 10 different war titles, but I still beat his ass and made him my bitch. The same goes for Arihama, now the only thing missing is a good sex scene to dick down Arihama and teach him his place, before sending him off to the void/completely destroying him.