with the new multi-body functionality, introduced in Creo 7, you have the option to select a body and RMB "create part from body".
this is significant enhancement.
In order to complete the designer need two option are missing:
1. having the possibility to select multiple bodies from tree/screen RMB "Create ASM from bodies". the outcome of this should be an assembly with each body defined as a part and located at the relevant location ( according to geometry placement in part )
2. each part should have the geometry as a features rather than external geometry feature.