Hi Cynefrid,
Mass Upload is possible through custom code written ABAP other that the currently followed LSMW or BDC approach. I have researched on a Function Module approach and have put down the same in the document http://scn.sap.com/docs/DOC-58974.
An ABAPer who goes through the paper will have a fair idea on how to implement the same and get it working.
Hope it helps.
Reward Points if helpful!
Regards,
George Abraham