Mhm, I have already thought about that, too. A simple way to do it would be to create an "SPAnimatedSprite", which is just a normal sprite with a juggler.
For now, I recommend you just make such a class yourself and use them in your games! It's not much code.
Another alternative I am considering is making access to the stage juggler easier. It's not 100% clean, as there could potentially be more than one stage in an application, but I think in this case it would make sense to add singleton access to the stage, like this:
[SPStage mainStage];
This would make it possible to access the stage, and thus the juggler, even in "init"-methods:
SPJuggler *juggler = [SPStage mainStage].juggler;
[juggler addObject: ...];
Expect something akin to this in Sparrow 1.1