A force rebuild doesn't update the bounding box?
Anyway, you can traverse all components in an assembly using IAssemblyDoc::GetComponents. You can fold and unfold by suppressing the sheet metal fold pattern feature, which can be accomplished via the API using IFeature::SetSuppression2.
For the first part, I have a macro that can get you started. See "Run code on every part in assembly" in our Macro Library. Requires a free membership.
Thank you for your insight in this Keith. I will be trying to implement something soon.
A force rebuild does not update the bounding box unfortunately.