I'm thinking something like this...
Leave the combined shell as-is (i.e. not deleting it) and treat it as a "gestalt-figure", labeling it both "gestalt" and "figure", and plopping it into the existing group. We'd then create the two parts for the two halves of the shell and add them to the group.http://www.shmax.com/product_details/1802/cloudburst
It would pretty much look the same, except the shell would be on the right side, along with the figure, and of course, we'd have two new parts (mold halves).
What would need to be done though is, since "gestalt" figures don't have mold numbers, is to assign that mold number that was previously assigned to the combined shell form, to one of the new shell halves we would end up creating.
Speaking of forms...what would we label these halves? Continue to just call them "human" or "bear"? If so, we end up skewing data associated with each. Say we had 23 pieces that had a bear form before...now, we're gonna end up with 25, even though each part is technically half a bear. Or do we call them something ambiguous like "pretender shell half" for form?