Hello Vilas,
Can understand your confusion. Still looking for all the right terms and so on.
In short; in the SAP document it is mentioned that you can post your data directly from ECC to ASN. Another option is to do this through PI. As the client saw this they wondered if it was possible to send the data to PI. And instead of then sending it to ASN would it be an option to sned the cxml document directly to the supplier.
But as Andreas mentioned "Ariba's cXML won't help you when there is no Ariba Network involved - See more at: http://exchange.ariba.com/communications#sthash.y6gIJEuh.dpuf", I think we need to conclude that the client's idea won't work.
Regards,
Timo