So my question is: Is there anyway to get within the context of an APEX session within a resource template?
Alternatively support for uploading files/blobs through an APEX context would be even better. e.g. p_blob001
No there isn't any way to do this, but supporting multiple file uploads in APEX seems like a possible feature enhancement, I would recommend reaching out to the APEX team to describe your use case, and see if they have any recommendations.