While Alucard completely respects everyone else's arguments and agrees with the majority of them, he would additionally propose the benefit for their respective peoples. Not just in the overall cultures and how they can help each other (one clan's military, another's arts), but also in their safety, security, and the people's happiness.

Overall, neither clan want war, despite some of the rebels that instigated the coup with Empress Nama. A handful of rebels does not voice for everyone. In order to protect both kingdoms, it's best to unify them.

I don't have a fully proposed argument yet but once I get my brain in order I'll put something together.