Currently all operations from the Dynamics 365 Portal are executed as the SYSTEM user. This means, that for any organization where data generated from the portal must belong to a specific business unit, must rely on custom functionality in order to assign ownership correctly. Additionally, functionality specific for the business unit or business area being covered by the Portal, cannot rely on actions being executed as a specific user. Currently all Portal actions looks the same, no matter the number of Portals. I suggest allowing organizations to pick which systemuser should be the principal user for all actions being executed by any one Portal instance.