i was actually going to post a similar thing...
i think the Legion would have been a better set-up than the "Freak of the Week" that's gotten over done...even this week's episode...MORE Kryptonite? It's more common than gold!
The way i wouldhave done it is have the Legion show up over season 1 as observers...some times "obvious", in the shadow, maybe sometimes as a student who's a recurring character.
They might even make contact with Clark's parents first, and THEY conspire together.
After a couple of seasons, they could drop the Legion, and run with the other characters.