"would an eU army prevent scum like Blair to dive head long in it without involving EU in it?"
The answer still remains absolutely not. The EU Defence force (it upsets people to call is an 'Army' so in deference, Ill use the terminology the EU are using) is being raised as an additional military force, to embark on operations specified by Brussels, not a replacement for national forces.
Though of course to maintain both, means a nation state will have to raise its defence spending to meet the additional 40billion the EU are spending on this, or they transfer some of its current defence spending to the EU.
As I pointed out earlier, we will know more about their proposed operations in 3 months time.
But in short, any nation state can and will always be able to take steps to 'defend' itself. That was the fundamental ethos behind the Bush/Blair position, and its an ethos even the EU wont meddle in.
There are hundreds of reasons why an EU Defence force is a really bad idea, but the one that should concern you the most, is that the EU have a very nasty habit of disregarding their own treaties and laws.
Take the bail-out situation for example. Article 125 of the Treaty on the Functioning of the European Union, is the no bail-out clause. None. No bail out of any member state. Ever. Yet off they go, bailing out. Then apply that utter disregard, to military action from a combined military force commanded from Brussels.
Blair at least had to seek approval from parliament before taking us to war, (though as we now know he lied), but the EU council have form when it comes to telling you one thing, backing it up with legal, expensive, time consuming legislation, then simply ignoring it at will.
The treaties arent worth the paper theyre written on, and neither will the assurances they give regards an EU Defence force.
(I wont go into the other 134 reasons I have, its getting late and its time for 
)