From the sound of--perhaps a COMBINED approach might be more profitable? Something like Morphs on the head, Bones controlling breast movements and a Magnet for the belly?

I'd say it depends on the actor division of the figure and what exactly you want to accomplish.

A couple of magnets won't be that big of a resource hit.

I cannot save the world. Only my little piece of it. If we all act together, we can save the world.--Nelson Mandela
An  inconsistent hobgoblin is the fool of little minds
Taking "Just do it" to a whole new level!