I have kind of the same question but mine is Oracle MRP. We use Smarteam as our PDM and it's an Oracle Sequel database so I'd think it would be a matter of just linking some tables somewhere.
Good luck, I'll keep watching here...
You would want to look into Cideon, which has the PLM integration into SAP. Currently, that is best way I believe to connect your files with SAP. However, it sounds like you are looking for a more direct connection with no PDM system, but I would shy away from anything home-grown or too lightweight to understand all the data and keep it connected properly.