That's very short term thinking. If you capture someone alive they can be interrogated. There's lessons to be learned about the process of radicalisation if nothing else.
I would guess there are already think tanks that have delved into the supposed arcane process of radicalization of a Muslim in Europe, specifically France.
Perhaps, the "lessons to be learned" is better learned by any future radicalized Muslim that hates European soldiers and Jewish children. The lesson might be, in my opinion, is that one might be signing one's own death certificate if one decides to bring the hatred of the Middle East to Europe by "acting out" in such an unlawful manner.
In other words, radicalized Muslims should learn to "thumb their noses" at those they dislike. Maybe a loud "Harumph" would be acceptabe also. We wouldn't want radicalized Muslims to hold in any venomous emotions, so "thumbing one's nose," with a loud "Harumph" should be an adequate catharsis. Nothing more is really needed, if one understands that the hatred in the Middle East needs to stay there.
Perhaps, old episodes of Monty Python's Flying Circus could be viewed by alienated Muslims to learn the British art of showing displeasure, without resorting to illegal actions?
In my opinion, the lesson that immigrants in Europe might need to understand en toto, regardless of their level of alienation, or non-alienation, is that living in Europe requires civilized behavior. Period.