as you can see MASS only supports object BUS2000115, and this is not supported anymore, if you want to massively change Sales Orders you should do it via Web UI.
If you want to change the partners involved in activities, you have two options, create a custom program or use sxda+lsmw using the corresponding XIF interface (message CRMXIF_ORDER_SAVE_U06)
If you have more regarding the main topic of this threat, I'll be more than happy to try to help, otherwise kindly open a new threat.