Hi Matthias,
I checked in documentation and tried in lab as well to see if this functionality exists, I do not see any such functionality supported till EXOS 16.1. User accounts can be only be
1. Admin - With Read and write access
2. User - With Read only access
Do you want your requirement to be supported in later version of EXOS?
If yes, please open a service request with GTAC for feature request.
Thanks,Syed