What, Mighty Avengers? That's not like the old Avengers at all, as far as I'm concerned. The old Avengers would never have been Tony or SHIELD's goon squad.
Hence, me saying that it's "as similar to the old Avengers as is possible for Bendis."
As for Jan, I guess it might be because she's had arguably the most personal growth as an Avenger. She went from the ditzy, boy-crazy moron in the first year or two, overcame emotional and physical abuse, and eventually grew into a pretty solid leader.
She was a solid leader in one story. Now it was arguably the best Avengers story ever, but it was still only one story. And why Bendis likes her so much but has her do jack squat is beyond me.