Except that Brock and Dawn are BOTH sidekicks more or less.
No, Satoshi and Hikari are clearly equals while Takeshi is a sidekick.
And I'm looking at the Jirachi DVD on my shelf, and Ash, May, Brock, and Max are all on there. So is Jirachi (that movie's "cute Legendary").
Well maybe PUSA will put Brock on the final cover, but Piplup was referring to the Japanese cover where he's not present at all. And I think it's obvious Shaymin will be on the final cover.