Overall, it sounds like your argument *for* the EU rests on two premises...
1) That economic integration much be accompanied by political integration, and is a positive good. The latter is historically questionable - again compare European and Chinese history. The former point though is obviously false. The EU originated as primarily an integration of economic policy, and could have continued as such indefinitely.
2) That political unification is singularly important in preventing inter-European war. But there has not been a chance of war in Europe, excluding Soviet client states, since WWII when democratic governance was forced upon the defeated states.
Every state within the EU is already democratic (except for arguably Belgium). So, if the Rummel hypothesis is correct, and it is hard to argue otherwise, that the best way to prevent interstate and intrastate conflict is to encourage representative government, if anything, how does adding another layer of government effect likelyhood of interstate war in a positive manner?
As a specifically European model to consider, look to the history of Germany.
Founded in 1871, within two generations, the now unified state was fighting the worst war Europe had ever seen. Not against other Germans, true enough, but against other states none the less.
So, to return at the point at hand, it seems that neither of your arguments really provide a benefit to me. The first is achievable without surrendering anymore political authority, and the latter you already possess thanks to American and British post-WWII policy.