Hi
I don't think that could be possible as the billing documents are created with reference to SO/Del and the data is being refered and maintained in different Tables VBAK, VBAP, VBRK,VBRP etc.
Also in the SO user genrally enter Sold to Party and rest of the Partners are determined from the master data maintained for the same (Program- SAPMV60A).
What your trying to acheive require excisive program and data changes in the standard progrrams and Tables involved in the entire process which is not recomended SAP practice.