Hi Tomoe,
It's possible but landing on one specific technology is not necessarily going to give you the outcome you need.
Firstly Fiori - Fiori My Inbox supports both Business Workflow and BPM.
Secondly - Business rules
Suggest you at least consider DSM and BRFPlus in this space to provide your business rules
While BPM includes BRM, if the source data for your rules is held in a ABAP system, then DSM/BRFPlus may provide a more effective solution.
Both BRM and DSM/BRFPlus can be integrated with Business Workflow and BPM
Thirdly workflow based process control
- you don't mention your specific concerns around using workflow? That might help to decide which way to go
- BPM or Workflow are both possible
Workflow is strong where the process is entirely within one SAP instance/system
BPM is strong on cross-instance/system scenarios but can handle single instances as well
Often BPM would be used with Process Orchestration as part of broader approach
There are differences in how the different technologies build their flows, handle events and handle read/write to business data
Also there are differences in the resources and skills you will need
So the question you are asking needs a nuanced answer that looks at your whole situation, and the final answer may be a combination of multiple technologies.
Suggest you start with a getting a picture of what workflows you need to support, and what sort of user experience you want for the inbox. You may want to consider getting some roadmap/future direction advice via your local SAP Office before going too far down one path or another.
Rgds,
Jocelyn