Well I am amazed that irrespective of anything else, ANYBODY can board a long haul flight with NO baggage in the current climate and not be subject to intense questioning. After AA security referred him back to the French police, who we know don't have the best reputation in the world (try going to them if you are a tourist and have an incident in France!), and the police found "nothing wrong" I can't believe that nobody at AA was still suspicious.
As mentioned a reroute would be good. Inform all the flight and cabin crew. And now a full change of clothes seems likely.
This guy didnt look too clever, and the fact that he could have gone to the toilet and light the fuse undisturbed and successfully caused a disaster, but didnt shows he was a bit dim. It's just a matter of time before one of his colleagues with an IQ higher than 15 tries his luck, and that is worrying.
I hear stories of all kinds of (innocent) people being offloaded due to a perceived threat, yet the shoe guy after causing MUCH justified suspicion was eventually welcomed on board.
Watch out!!