Well, thanks for the effort anyway man!
Okay -- I have something. (BTW I can't reach you on your hotmail email for some reason)
I changed the g2png.py code -- hacking like a blind monkey without savvy It will now save ALL groups on a named layer (defaults to 'slices') out to a single PNG. I called it lg2png cos it's "Layer of Groups to Png"
I re-read your OP and I'm not really sure what you want it to do; I hope this one does it but, if not, you can use this new script along with the original to get some idea.
How to install: (I assume Linux, but Windows should be similar) 1. Copy the attached 2 files into : /usr/share/inkscape/extensions (I assume that's standard, check first). You will need to sudo copy them. 2. Restart Inkscape. 3. Done. 4. Test ( I haven't really tested it much) Good luck, HTH, I gotta get on with other stuff now.
/d PS - If the attachments don't get through to the list, please let me know where to send them.