I said the same thing about the clones, who is that guy? Of course, Han and Luke both wore storm trooper armor(albeit, a little ill-fittingly). I do think the lightsaber looked cool. why is it implausible?
My first impression when disney bought this was that they will probably make some entertaining films. Not great, like episodes 4,5,and 6, but more enjoyable than 1,2, and 3, though I think I rank those prequels higher than most. I know, I know Jar Jar Binks, and both actors who played Anakin were terrible, but I liked them, and the insight they gave to the whole story, even if they lacked in certain areas. Let's face it, Mark Hammel was awful whiny, and the cheese between him, Leia and Han was stinkier than much of what comes out of France. Go disney!
The lightsaber "looks" kinda cool, but from a dueling standpoint it would be impractical. The crossguard is intended to stop a blade from sliding down yours and cutting into your hand. If you look at the design, there is a metal crossguard with short plasma blades emitting from it. If another saber was to hit the crossguard in the manner it was intended to be used, it would not be hitting the plasma, but the metal. You are looking at a small piece of handle material trying to stop a plasma blade that will cut fully into a blast door. Darth Maul's double ended sabre getting cut in half shows that. So now you have something with the potential to cut your own hand off that won't do what it was intended to do.
Only in the beginning of the Empire were the stormtroopers still clones, a holdover from the clone armies of the Republic. Eventually they were phased out, and normal soldiers were recruited instead.
That was the simplest explanation I could possibly give, but this link should clear it right up
http://starwars.wikia.com/wiki/Stormtrooper
I stand corrected on the storm trooper. I didn't read all of the books, and wasn't aware of that bit.