The moment you touch anything related to accounting or subject to laws / regulations, stuff gets very hairy.

There might be more offered by SAP than you are accounting for. You would have to re-create all of the features for things like demand management aggregated forecasting by product line, including integration with supply chain ordering and EDI integration with your global suppliers and customers. You might also need a solution for maintaining separate general ledgers for local hyperinflationary accounting requirements in Brazil in parallel with GAAP reporting in the US. And those other services such as HR and invoicing...they are also all in the box with SAP if you choose to go whole hog.

OpenERP is not Django based IIRC, but they basically thought the same thing and went at it with some good success.

I seriously doubt OpenERP has the same scope as SAP. It works for smaller structures but, like mentioned before, if your operations cross too many national borders, things get insanely complicated really quickly.

That is one hell of a Django app.