i am not entirely sure if i got you right. But woudnt it be a solution to just export an IDML file out of your CS6 document and hand that out to the other person?
I mean, skip the REpackaging part and just sent that IDML file over…
Just add the .idml fiel to the package you already made. I'd include a PDF as well so they have a clue what the layout looked like originally since it might look a bit different when opened in CS5. This is not a good workflow.
There is no such function in InDesign as 'saving to a lower version' (as it is in e.g. FrameMaker). There are interchange formats: obsolete INX (CS2,CS3,CS4) and current IDML (CS5, CS5.5, CS6).
You need to export (ctrl+e) previously saved document into IDML and attach to existing INDD file (Attaching is not necessary as IDML is a self-sufficient file). Also it's a really good idea to attach a PDF file (from CS6) as there might be some differences when opening a IDML from higher file in lower version program.
Final package could look like this:
the .idml option has been added to the Save As menu in CS6, though technically it is still an export.
First package the file. Close it. Then open the INDD file in the package. Choose file save as and save it as InDesign CS4 or later (IDML).
Benefits of this are the IDML will find the links in the links folder and when you do the save as, it will automatically go to the folder that the INDD file is in. The export will save to the last folder you exported to.
Once again, Peter and Bob have given excellent advice. This is exactly what you should do. And this is coming from someone whose company only JUST NOW upgraded, a year after the release of CS6. The way they are telling you to do it is the way that a company requiring CS5 files would prefer to receive them from someone running CS6. Kudos Peter and Bob.