What is the author's attitude?
Your speculation – that Shaw is saying that War and Marriage share many traits, is not far-fetched, but not as fruitful as other lines of inquiry. The title, taken from Virgil, hints at the real dramatic conflict on Shaw’s mind here: there is a difference between the outward signs of integrity and the real structure of the person inside. (Without going into The Aeneid too deeply, what looks like Aeneus’ lust for power is really his desire for Dido.)As Bluntschi and Sergius act, the truly heroic and the cowardly separate and Raina’s heart goes, not to the “false soldier” but to Bluntschli, the “man” who appeared to be cowardly. So the central concept is this difference. But your idea takes on weight when we note that the same “falseness” is evident on the courtship level – Sergius, even though engaged to Raina, flirts with Louka. But marriage as a war is not a main theme here, and there is no hint that Bluntschli and Raina will have a war-like union. As for Shaw’s attitude, he was quite unromantic in his opinion of Love. (When a beautiful actress suggested that they would make a beautiful baby -- “with my looks and your brains,”-- he responded “Yes, but what a disaster if it had my looks and your brains!”)