Those 2 DBZ Specials (Bardock, and History of Trunks) was what I was thinking of when I said that actually.
That and the first Digimon movie (the one where Tai first met Agumon when he was a kid)...didn't want to use Digimon as an example...
...but yeah, it'd be cool.
Edit: But really, Y's point makes more sense to me now. There's a good chance of another writer besides Kishimoto interfering with the series continuity with a project like that.