This is my first post here and I hope it will be useful. I wrote a small python script that might be useful to anyone who wants to automate the batch-export of a list of objects.
The script can be configured to export list of object (using their ids) from multiple files with different dpi (which for the moment can not be achieved in the user interface).
Inkscape is launched in shell mode so only one instance is started which should improve performance. The script is available here: https://gist.github.com/lzubiaur/9074270
Any comments or suggestion are welcome!

Regards, Laurent