I have never seen a 7-starter set that started on any of the stages past the original five-starter list; in fact, I've rarely seen a set start on Lylat or Yoshi's either.
And can you please tell me what's wrong with stages like Green Hill Zone and Mario Circuit if they were simply banned as counterpicks for chaingrabbers?
Mario Circuit: Cars. Also a small circle, though not quite as complete as a true circle has to be (i.e. solid wall).
Green Hill Zone: Checkpoints, disappearing stage (This wouldn't be an issue, except that the stage disappears at the start of the animation, but you can't tell the animation is happening until about 1/3 of the way through it).
Neither of the stages is CP-worthy even ignoring CGs.
Chaingrabbing is an unbeatable strategy. If you get grabbed, you've lost your stock. That's why it's banned.
I fail to see why this logic can't be applied to Jungle Japes, seeing as D3 can time a grab release into klaptraps fairly easily; that's another can of worms, though.