The main problem is not only handle the cXML (that is just a different format o a standard XML and can be achieved with the standard functions in BC) but the entire punch-out flow, with the correct configuration for message setup on the supplier system and manage the response in BC (and this is the most diffcult part due to the security).

I don't want to go deep in detail on how the punch-out works but this is already available on other Microsoft Dynamics ERP products so it can be really usefull to have the same available in Business Central.