Hi CMPT,
Yes, you can configure a BRF+ decision table to identify User Default IDs based on target system, user group and other access request attributes.
The User Default IDs are based on the target system and can be set up in SPRO.
Please have a look at the details mentioned here: Setting up User Defaults in Access Control 10.0 - Governance, Risk and Compliance - SCN Wiki
BR
Sebastian