I haven't seen the idea to split amp models into pre and power amp blocks to enable a virtual FX loop, mixing and matching diff pre's and power sections, etc, so I created a new entry in IdeaScale:
http://line6.ideascale.com/a/dtd/Independent-pre-and-power-amp-blocks/748793-23508?submitted=1
I understand cabs are already their own independent blocks, but if this is not the case, please let me know.