Frankie Edgar was the world champion at lightweight, he doesn't need to drop to featherweight. Saying that he's simply "too small" to fight at lightweight borders on blindly idiotic.
Frankie Edgar is 14-2-1 as a lightweight. He even beat B.J. Penn—the man who is considered to be the greatest lightweight of all time—two times, once to win the UFC lightweight title and then a second time to defend it.
And those weren't bad decisions, Edgar was more nimble, beat Penn to the punch, and was just the better fighter over all.
"So! Penn was demotivated," you say?
Then let's move on to Gray Maynard.
Maynard was significantly bigger than Edgar and had already beaten Edgar once yet when they fought for a second time, Maynard couldn't finish him; the fight ended in a close draw.
In the third meeting between the two men (and the second title fight), Edgar actually managed to knockout the larger Maynard, showing that Edgar's size is NOT the detriment that people are making it out to be.
Even in the fight against Benson Henderson at UFC 144, the smaller Edgar managed to land five takedowns compared to Henderson's one.
Even though Edgar was on the losing end in strikes landed, he showed that he belonged in the cage with Henderson and that he belongs in the cage at 155 pounds.
Saying that Edgar is too small is absurd. The man was big enough to win a world title and he's big enough to do it again at lightweight.