How to use BCS in Word for editing BLOBs

If I have an External Content type defined with a StreamAccessor t开发者_JAVA技巧hat will end up referencing Word docx files stored in another system (reason for using BCS), what options do I have for updating the docx file? I'm aware of the ability to expose a BLOB using the stream accessor and WebParts to open up Word (assuming the BLOB is a Word docx), but do I have to use some custom VSTO solution or the BDC client runtime from Word in order to write back changes?

Any ideas are welcome.